Antenna device and wireless terminal using the antenna device

ABSTRACT

The present invention aims at providing an antenna apparatus which enables switching directivity suitable for a plurality of usage patterns of a wireless terminal, such as that achieved during voice conversation and that achieved during data communication, and is easily slimmed down, as well as providing a wireless terminal using the antenna apparatus. 
     An antenna apparatus  1  of the present invention includes a linear radiating element  3  placed on a first plane; a first parasitic element  6  placed on the first plane in parallel with the radiating element  3 ; a first ground conductor  5  placed on the first plane; a first switch  7  which connects both ends of the first parasitic element  6  to the first ground conductor; and a second ground conductor  8  placed on a second plane opposing the first plane, wherein a part of the first ground conductor  5  is placed in parallel with the radiating element  3  and on a side opposite the first parasitic element  6  with the radiating element  3  sandwiched therebetween; and the second ground conductor  8  is placed opposite the radiating element  3 , and ends of the second ground conductor  8  oppose an area sandwiched between the radiating element  3  and the first parasitic element  6.

FIELD OF THE INVENTION

The present invention relates to an antenna apparatus and a wirelessterminal having the antenna apparatus built-in, and more particularly,to a wireless terminal having a built-in antenna having the function ofelectrically changing a directional characteristic.

BACKGROUND ART

Recently, in the field of a wireless terminal such as a cellular phoneor the like, demand has grown for a data communications function inaddition to a voice conversation function, and a wireless terminalhaving both the voice conversation function and the data communicationsfunction has become prevalent. In the case of a wireless terminal havingboth a voice conversation function and a data communications function, apositional relationship between the wireless terminal and a user whouses the wireless terminal changes between the case where voiceconversation is performed and the case where data communication isperformed.

For instance, in the case of voice conversation, the user uses awireless terminal such that the terminal is pressed against one of theuser's ears, as can be seen from FIG. 10, which shows an examplepositional relationship between the wireless terminal and the user whichis adopted during voice conversation. Accordingly, the wireless terminalis used while being positioned on the side of the user's head. Incontrast, in the case of data communication, the user ascertainsinformation appearing on the display of the wireless terminal as can beseen from FIG. 11, which shows an example positional relationshipbetween the wireless terminal and the user which is adopted during datacommunication. For this reason, the wireless terminal is used whilebeing positioned at a distance from the front of the user's head.

As mentioned above, when the positional relationship between thewireless terminal and the user who uses the wireless terminal changesbetween the case of voice conversation and the case of datacommunication, the directional characteristic of the antenna apparatusbuilt-in the wireless terminal is required to be changed to oneappropriate to the positional relationship. FIG. 12 specifically showsan example radiation directivity of the antenna acquired during voiceconversation and that acquired during data communication.

For instance, a unidirectional antenna is required to be configured soas to be able to switch directivity such that, when the wirelessterminal is placed on the side of the head as in the case of voicecommunication, the maximum radiation direction of the antenna is towardthe back of the wireless terminal; and such that, when the wirelessterminal is placed at a position distant from the front of the user'shead as in the case of data communication, the maximum radiationdirection of the antenna toward the zenith direction of the wirelessterminal. In short, the antenna apparatus built-in the wireless terminalis desired to be unidirectional and have a configuration which enablesswitching of the maximum radiation direction of the antenna achieved inthe respective usage patterns; namely, during voice conversation anddata communication, from the zenith of the wireless terminal to the backof the wireless terminal.

By means of the configuration of such an antenna apparatus, theorientation of a radiation field from the antenna apparatus to the humanbody is prevented, so that an SAR (Specific Absorption Rate) can beenhanced. Further, since electromagnetic radiation in an unnecessarydirection is prevented to thus achieve unidirectivity, an attempt toenhance an antenna gain can be enabled.

For instance, an antenna configuration which switches the directivity ofa Yagi antenna to and fro by means of controlling the length of aparasitic element through use of a control element has hitherto beenproposed as an antenna configuration capable of switching thedirectivity of the antenna (see, e.g., Patent Document 1).

FIG. 46 is a schematic diagram of a related-art directivity switchingantenna described in Patent Document 1. In FIG. 46, reference numeral101 designates a pair of parasitic elements; 102 a feeder element; 103an auxiliary element; and 104 a control element.

Operation of the related-art directivity switching antenna described inPatent Document 1 will be described hereinbelow. The parasitic elements101 are placed, in a related-art directivity switching antenna, at givenintervals from the feeder element 102 in the lateral direction thereof.Each of the parasitic elements 101 is configured so as to enable thecontrol elements 104 to connect the auxiliary elements 103, which areadditionally provided in an electrically-insulated manner, to the endportions of the parasitic element 101. The control element 104 is formedfrom a diode switch, or the like, and attached in such a way that thecontrol element 104 is brought into conduction with one of the parasiticelements 101 and the auxiliary elements 103 provided at the respectiveends thereof.

Consequently, when a positive voltage has been applied to the parasiticelements 101 via a lead wire, one of the parasitic elements 101 isbrought into conduction with the auxiliary elements 103 provided at therespective ends thereof, to thus act as a reflector. The remainingparasitic element 101 is not brought into conduction with the auxiliaryelements 103, to thus act as a director. Therefore, the antenna ofPatent Document 1 exhibits directivity in the direction of the parasiticelement 101 that remains out of conduction with the auxiliary elements103. When a negative voltage has been applied to the parasitic elements101 via the lead wire, the positional relationship between the parasiticelement 101 operating as the reflector and the parasitic element 101acting as a director is reversed, and hence directivity is alsoreversed.

By means of adoption of the above configuration, the Yagi antenna, whichcan reverse directivity through 180° by means of simple control; i.e.,switching of the polarity of a voltage applied to the parasitic elements101, can be configured.

There has also been proposed an antenna configuration where an antennaelement is placed upright on a bottom board and parasitic elements areprovided around the antenna element and which switches directivity bymeans of switching the function of the parasitic element between adirector and a reflector (see, e.g., Patent Document 2).

FIG. 47 is a schematic view of a related-art directivity switchingantenna described in Patent Document 2. In FIG. 47, reference numeral111 designates a bottom board; 112 a radiating element; 113 to 116parasitic elements; and 117 to 120 dielectric substrates.

Operation of the related-art directivity switching antenna described inPatent Document 2 will be described hereinbelow. The radiating element112, which acts as a radiator, is placed on the bottom board 111realized by the dielectric substrates 117 to 120. The parasitic elements113 to 116, which act as reflectors or directors, are mounted on thedielectric substrates 117 to 120. The dielectric substrates 117 to 120are placed upright on the bottom board 111.

The bottom board 111 is equipped with switching circuits for switchingthe functions of the parasitic elements 113 to 116 between reflectorsand directors. One of the switching circuits is short-circuited to thusopen the other switching circuits, thereby imparting directivity to theantenna. For instance, the switching circuits are selected in such amanner that the parasitic element 113 is caused to act as a conductorand such that the other parasitic elements 114 to 116 are caused to actas reflectors, whereby the directivity of the antenna can be orientedtoward the parasitic element 113. Likewise, any one of the switchingcircuits of the parasitic elements 114 to 116 is short-circuited, tothus enable switching of directivity to any of four directions arrangedat 90° intervals.

By means of the above configuration, there can be constituted an antennawhich can switch directivity at intervals of 90° by means of simplecontrol; i.e., inducing a short circuit to open the switching circuits.Further, the parasitic elements 113 to 116 are formed on the dielectricsubstrates 117 to 120. Hence, the dielectric constants of the dielectricsubstrates 117 to 120 are increased, so that the lengths of theparasitic elements 113 to 116 are reduced by means of the effect of areduction in wavelength. Thus, an attempt to reduce the profile of theantenna can be enabled.

An other proposed configuration of the antenna apparatus capable ofswitching directivity thereof is, for example, to divide an earth metalconductor into two subdivisions and change the electrical length of theoverall earth metal conductor by means of a switch, thereby switchingdirectivity (see, e.g., Patent Document 3).

FIG. 48 is a schematic view of a related-art directivity switchingantenna described in Patent Document 3. In FIG. 48, the directivityswitching antenna comprises an antenna element 301; a matching circuit302 for matching the antenna element 301 with a receiving circuit 303; areceiving field intensity comparator 304 for effecting comparison ofintensity of a signal delivered from the receiving circuit 303; acontrol circuit 305 for activating and deactivating a high-frequencyswitch 308; earth metal conductors 306 and 307 divided into twosub-divisions which are connected in series to the antenna element 301and correspond to the earth conductor of the antenna apparatus; and twohigh-frequency switches 308.

Operation of the related-art directivity switching antenna described inPatent Document 3 will now be described. An electromagnetic wavereceived by the antenna element 301 is delivered to the receivingcircuit 303 by way of the matching circuit 302. Further, the controlcircuit 305 controls the high-frequency switch 308 such that thehigh-frequency switch repeats activation and deactivation at arbitrarytime intervals. As shown in FIG. 49( a), when activated, thehigh-frequency switch 308 exhibits radiation directivity which issubstantially perpendicular to the antenna element 301. As shown in FIG.49( b), when deactivated, the high-frequency switch 308 exhibits adirectivity characteristic having a radiation directivity characteristicof about −30° as compared with the case where the high-frequency switch308 is activated.

By means of the above configuration, the lengths of the earth metalconductors 306, 307 serially connected to the antenna element 301 areelectrically changed by the high-frequency switch 308, so that two typesof antenna directivity characteristics can be obtained.

An other proposed antenna configuration is to place antenna reflectorsat rear right and left positions with respect to the antenna element andto control ground impedance of the antenna reflectors, to thus switchdirectivity (see, e.g., Patent Document 4).

FIG. 50 is a schematic view of a related-art directivity switchingantenna described in Patent Document 4. In FIG. 50, the directivityswitching antenna comprises an antenna 311, an antenna element 312,antenna reflectors 313, 314 which are disposed at right and leftpositions with reference to the antenna element 312 and are each formedfrom a substantially triangular conductor plate, and a mold 315 forcovering the antenna 311.

Operation of the related-art directivity switching antenna described inPatent Document 4 will now be described. The antenna reflectors 313, 314are provided at lower right and left positions with reference to theantenna element 312 and connected to a ground impedance circuit forimpedance variation purpose provided on a substrate of the wirelesssection. FIG. 51 is a characteristic view showing a change in thecharacteristic of the antenna acquired when switching between theantenna reflectors 313 and 314 is performed. Switching between theantenna reflectors 313, 314 is performed by means of grounding either ofthem.

Moreover, the directivity of the electromagnetic waves radiated from theantenna element 312 is switched by means of the antenna reflectors 313,314 that are connected to the ground by way of the ground impedancecircuit, to thus realize a diversity function. When switching betweenthe antenna reflectors 313, 314 has been performed to thus select theantenna reflector 314 as a ground-side reflector, directivity of theantenna element 312 interferes with the antenna reflector 314 as shownin FIG. 51( a), to thus exhibit rightward directivity. Conversely, whenthe antenna reflector 313 has been selected, the directivity of theantenna element 312 interferes with the antenna reflector 313 as shownin FIG. 51( b), to thus exhibit leftward directivity.

By means of the above configuration, directivity can be switchedleftward or rightward through 180° with respect to the antenna element312 by means of a simple method for controlling the ground impedancecircuit connected to the antenna reflectors 313, 314 to thus ground oneof the antenna reflectors.

-   Patent Document 1: JP-A-6-69723-   Patent Document 2: JP-A-2001-345633-   Patent Document 3: JP-A-5-48506-   Patent Document 4: JP-A-2001-292017

DISCLOSURE OF THE INVENTION Problem to be Solved by the Invention

However, by use of the configuration such as that described inconnection with Patent Document 1, conductor patterns can be formed on,e.g., the dielectric substrates 117 to 120. Hence, the antenna apparatusis suitable for being built in the wireless terminal. Since directivitycan be switched to and fro merely by 180°, there has been a problem ofdifficulty in realizing directivity of an antenna apparatus suitable forthe usage pattern of the wireless terminal achieved during voiceconversation and that of the wireless terminal achieved during datacommunication.

By use of a configuration such as that described in connection withPatent Document 2, directivity of the antenna can be switched atintervals of 90° by means of switching of the switch. However, in orderto effect switching between the zenith direction and the back directionof the wireless terminal, the bottom board 111 must be provided at rightangles to the dielectric substrates 117 to 120 provided in the wirelessterminal. Hence, difficulty is encountered in reducing the profile ofthe wireless terminal.

By use of a configuration such as that described in connection withPatent Document 3, the earth metal conductor can be formed from aconductor pattern on, e.g., the enclosure or the dielectric substrate,whereby the electrical length of the earth metal conductor can bereadily changed to thus change directivity. However, the earth metalconductor must be connected in series to the antenna element. Hence, theconfiguration has the problem of being applicable solely to a monopoleantenna element and being inapplicable to an antenna element of a dipoleantenna balanced feeding system.

An antenna reflector is formed within an antenna enclosure by use of aconfiguration such as that described in connection with Patent Document4, so that the antenna element can be incorporated into the wirelessterminal. The antenna reflector can be applied, as an antenna element,to an antenna element of a balanced feeding system, such as a dipole.However, directivity can be switched rightward and leftward by merely180°. Accordingly, there exists a problem of a failure to realizedirectivity of the antenna apparatus suitable for each of the usagepatterns of the wireless terminal acquired during voice conversation anddata communication.

The present invention has been conceived in light of the above situationand aims at providing an antenna apparatus capable of switchingdirectivity suitable for a plurality of usage patterns of a wirelessterminal, such as that achieved during voice conversation or thatachieved during data communication, as well as providing a wirelessterminal using the antenna apparatus.

Means for Solving the Problem

An antenna apparatus of the present invention comprises a linearradiating element placed on a first plane; a first parasitic elementplaced on the first plane in parallel to the radiating element; a firstground conductor placed on the first plane; a first switch whichconnects both ends of the first parasitic element to the first groundconductor; a second ground conductor placed on a second plane opposingthe first plane; and control means for controllingshort-circuiting/opening of the switch, wherein a part of the firstground conductor is placed in parallel to the radiating element and on aside opposite the first parasitic element with the radiating elementsandwiched therebetween; and the second ground conductor is placedopposite the radiating element, and ends of the second ground conductoroppose an area sandwiched between the radiating element and the firstparasitic element.

An antenna apparatus of the present invention comprises a linearradiating element placed on a first plane; a first linear parasiticelement placed on the first plane in parallel to the radiating element;a linear auxiliary element provided at both ends of a longitudinalimaginary extension of the first parasitic element; a first groundconductor placed on the first plane; a first switch which connects bothends of the first parasitic element to the auxiliary element; and asecond ground conductor placed on a second plane opposing the firstplane, wherein the first ground conductor is placed in parallel to theradiating element and on a side opposite the first parasitic elementwith the radiating element sandwiched therebetween; and the secondground conductor is placed opposite the radiating element, and ends ofthe second ground conductor oppose an area sandwiched between theradiating element and the first parasitic element.

In the antenna apparatus of the present invention, the first groundconductor is a linear conductor which is longer than the radiatingelement.

An antenna apparatus of the present invention comprises a linearradiating element placed on a first plane; a first linear parasiticelement placed on the first plane in parallel to the radiating element;a second linear parasitic element which is provided on the first planeopposite the first parasitic element with the radiating elementinterposed therebetween, and in parallel to the radiating element; alinear auxiliary element provided at both ends of longitudinal imaginaryextensions of the respective first and second parasitic elements; afirst switch and a second switch which connect both ends of the firstand second parasitic elements to the auxiliary elements provided on bothsides of the respective first and second parasitic elements; and asecond ground conductor placed on a second plane opposing the firstplane, wherein the second ground conductor is placed opposite theradiating element, and one end of the second ground conductor opposes anarea sandwiched between the radiating element and the first parasiticelement, and the other end of the second ground conductor opposes anarea sandwiched between the radiating element and the second parasiticelement.

The antenna apparatus of the present invention includes a firstsubstrate having one surface on which the radiating element, the firstand second parasitic elements, the first ground conductor, and the firstand second switches are provided, and another surface on which thesecond ground conductor is provided.

The antenna apparatus of the present invention further comprises controlmeans for controlling short-circuiting/opening of the switches.

When a usage pattern of the wireless terminal changes from voiceconversation to data communication, a related-art antenna apparatuscannot change the maximum radiation direction of the antenna to adesired direction according to the usage pattern. Thus, the antennaconfiguration has not been suitable for the wireless terminal. Accordingto the above configurations, on the other hand, when the switches areshort-circuited, the parasitic element operates as a ground conductor,thereby covering the surroundings of the radiating element with theground conductor. When the switches are opened, the parasitic element isdisconnected from the ground conductor, and hence directivity of theantenna can be switched to a desired direction by means ofshort-circuiting/opening the switches.

The antenna apparatus of the present invention includes a configurationwhere, when the switches are opened, the parasitic element acts as adirector with respect to the radiating element.

By means of this configuration, the parasitic element can be caused toact as a director. Hence, when the switches are opened, theconfiguration of a Yagi antenna can be formed from the radiating elementand the parasitic element. Directivity of the antenna can be switchedthrough about 90° while the switches remain short-circuited.

The antenna apparatus of the present invention includes a configurationwhere, when the switches are short-circuited, the parasitic element andthe auxiliary element act as a reflector with respect to the radiantelement.

By means of this configuration, the parasitic element can be switchedbetween the director and the reflector by means ofshort-circuiting/opening of the switches. Hence, when the switchesremain short-circuited, the directivity of the antenna can be switchedthrough about 90° without connecting the parasitic element to the groundconductor.

The antenna apparatus of the present invention includes the parasiticelement whose reactance is variable.

The antenna apparatus of the present invention includes the parasiticelement that is formed from switches used for connecting together aplurality of conductor pieces.

The antenna apparatus of the present invention includes the parasiticelement that is a variable capacity element.

According to the configurations, the electrical length of the parasiticelement can be varied. Hence, the directivity of the antenna achievedduring opening of the switches can be changed. Further, an inputimpedance characteristic of the antenna can also be adjusted.

The antenna apparatus of the present invention includes the substratethat is formed from a dielectric material.

By means of this configuration, the electrical length of the radiatingelement can be shortened by means of a wavelength-shortening effectinduced by the dielectric constant of the dielectric substrate. Hence,an attempt can be made to miniaturize the antenna.

The antenna apparatus of the present invention includes the substratethat is formed from a foaming material.

By means of this configuration, the radiating element, the parasiticelement, and the like are formed in such a manner that they can besubjected to sheeting. The thus-formed elements are fastened to thefoaming material, whereby a directivity switching antenna can bemanufactured in a very inexpensive manner.

The antenna apparatus of the present invention includes the radiatingelement that is folded in a horizontal direction with respect to thefirst substrate.

By means of this configuration, the input impedance of the radiatingelement can be enhanced. Even when the input impedance has become loweras a result of the ground conductor having been placed in the vicinityof the poles of the radiating element, matching to the feeding sectioncan be effected readily.

The antenna apparatus of the present invention includes the radiatingelement that is formed on the first substrate from a conductor pattern.

By means of this configuration, the radiating element and the substratecan be integrally manufactured, and hence inexpensive manufacture can becarried out. Further, an attempt can also be made to achieve a morestable characteristic.

The antenna apparatus of the present invention includes the secondground conductor that is formed on the first substrate from a conductorpattern.

By means of this configuration, the second ground conductor and thesubstrate can be integrally manufactured, and hence the end portion ofthe second ground conductor can be accurately positioned, and thecharacteristics can be made stable.

The antenna apparatus of the present invention includes the radiatingelement and the second ground conductor, which are arranged such that aninterval between the radiating element and the second ground conductorbecomes greater than the thickness of the first substrate.

By means of this configuration, the distance between the radiatingelement and the second ground conductor can be ensured. Hence,occurrence of a drop in the input impedance of the radiating element canbe prevented, and matching with the feeding section can be readilyachieved.

In the antenna apparatus of the present invention, the radiating elementhas a dipole configuration having a structure folded in a verticaldirection with respect to the substrate, and comprises a lower conductorplaced on the first substrate and folded sections placed on both ends ofthe lower conductor in an upright position with respect to the firstsubstrate, and an upper conductor disposed for connecting ends of thefolded ends.

By means of this configuration, the radiating element can be arranged ina three-dimensionally folded manner. Accordingly, the degree of designfreedom of the antenna is increased, and the area used for mounting theantenna can be reduced.

The antenna apparatus further comprises a second substrate provided onthe first substrate, wherein the lower conductor is interposed betweenthe first and second substrates; the folded section is provided so as topenetrate through the second substrate; and the upper substrate isprovided on the second substrate.

By means of this configuration, a radiating element having a foldedstructure can be formed by means of rendering a substrate multilayer.Hence, the antenna apparatus can be manufactured more inexpensively, andthe characteristic can be made more stable.

The antenna apparatus further comprises a dielectric block on the firstsubstrate, wherein the lower conductor, the folded section, and theupper conductor are provided on and/or in the dielectric block.

In the antenna apparatus of the present invention, portions of theparasitic element, the switches, and the first ground conductor areprovided on and/or in the dielectric block.

By means of this configuration, the radiating element and/or theparasitic element can be arranged in the dielectric block of a highdielectric material in a three-dimensionally-folded manner. Accordingly,the degree of design freedom of the antenna is increased, and the areaused for mounting the antenna can be made very small. Moreover, adielectric antenna having a directivity switching function can bemanufactured.

In the antenna apparatus of the present invention, the radiating elementcan be formed into a linear dipole.

According to this configuration, the radiating element can bemanufactured very simply. Moreover, the antenna can be formed into aYagi antenna configuration along with the parasitic element. Hence,switching of directivity through 90° can be achieved.

In the antenna apparatus of the present invention, the radiating elementis formed into a dipole having the shape of a meander line.

By means of this configuration, the radiating element can be made verysmall.

In the antenna apparatus of the present invention, the first and secondswitches are formed from diode switches.

In the antenna apparatus of the present invention, the first and secondswitches are formed from FET switches.

In the antenna apparatus of the present invention, the first and secondswitches are formed from MEMS switches.

By means of these configurations, the switches can be realized in a verysimple configuration. Further, the switches can be made very compact byuse of the MEMS technique. Hence, an attempt can be made to miniaturizethe antenna.

An antenna apparatus of the present invention comprises a linearradiating element placed on a first plane; a ground conductor placed ona second plane opposite the other surface of the first substrate; afirst conductor which is placed on the second plane while beingelectrically isolated from the ground conductor; and a first switch forconnecting the ground conductor to the conductor, wherein one of theground conductor and the conductor is placed opposite the radiatingelement.

The antenna apparatus of the present invention further comprises asecond conductor placed at a position symmetrical to the first conductorwith respect to the ground conductor; and a second switch for connectingthe ground conductor to the second conductor, wherein the groundconductor is placed opposite the radiating element.

The antenna apparatus of the present invention further comprises a firstsubstrate on which the first and second planes are provided.

The antenna apparatus of the present invention includes the groundconductor that is disposed opposite the radiating element.

The antenna apparatus of the present invention includes the conductorthat acts as a director with respect to the radiating element.

The antenna apparatus of the present invention includes the conductorthat is disposed opposite the radiating element.

The antenna apparatus of the present invention includes the conductorthat is longer than the radiating element.

When a usage pattern of the wireless terminal changes from voiceconversation to data communication, a related-art antenna apparatuscannot change the maximum radiation direction of the antenna to adesired direction through 90° according to the usage pattern. Thus, theantenna configuration has not been suitable for the wireless terminal.According to the above configurations, on the other hand, when theswitches are short-circuited, the first metal conductor operates as aground conductor. When the switches are opened, the first metalconductor is disconnected from the ground conductor, and hencedirectivity of the antenna can be switched to a desired direction bymeans of short-circuiting/opening the switches.

The antenna apparatus of the present invention includes that conductorwhose reactance is variable.

The antenna apparatus of the present invention includes that conductorhas a variable capacitance element.

In the antenna apparatus of the present invention, the conductorincludes a plurality of conductor pieces divided into a lengthwisedirection thereof and a third switch for connecting the plurality ofconductor pieces.

By means of these configurations, the electrical length of the firstmetal conductor can be varied. Accordingly, when the switches areopened, the directivity of the antenna can be adjusted. Further, theinput impedance characteristic of the antenna can also be adjusted.

In the antenna apparatus of the present invention, the conductorcomprises a plurality of conductor pieces divided into a widthwisedirection thereof, and a third switch for connecting the plurality ofconductor pieces.

By means of these configurations, the widthwise electrical length of thefirst metal conductor can be varied. Accordingly, when the switches areopened, the directivity of the antenna can be adjusted.

The antenna apparatus of the present invention includes the firstsubstrate that is formed from a dielectric material.

By means of this configuration, the electrical length of the radiatingelement can be shortened by means of a wavelength shortening effectinduced by the dielectric constant of the dielectric substrate. Hence,an attempt can be made to miniaturize the antenna.

The antenna apparatus of the present invention includes the firstsubstrate that is formed from a foaming material.

By means of this configuration, the first metal conductor, and the like,is formed in such a manner that it can be subjected to sheeting. Thethus-formed first metal conductor is fastened to the foaming material,whereby a directivity switching antenna can be manufactured in a veryinexpensive manner.

In the antenna apparatus of the present invention, the first switchcomprises a plurality of switches used for connecting the groundconductor to the first metal conductor at a plurality of locations.

In the antenna apparatus of the present invention, the plurality ofthird switches are provided in a symmetrical pattern with respect to aplane perpendicular to the radiating element including a feeding pointthereof.

In the antenna apparatus of the present invention, the third switchesare provided in an asymmetrical pattern with respect to a planeperpendicular to the radiating element including a feeding pointthereof.

In the antenna apparatus of the present invention, the third switchesconnect the ground conductor to the first metal conductor located at theposition opposite a neighborhood of the maximum voltage position on theradiating element.

These configurations eliminate a necessity for connecting the entireground conductor to the entire first metal conductor. Directivity can beswitched by use of the minimum required switches. Moreover, the switchesare short-circuited at positions which are asymmetrical with respect tothe lengthwise direction of the radiating element, wherebythree-dimensional switching of directivity becomes feasible.

The antenna apparatus of the present invention includes the radiatingelement that is formed on the first substrate from a conductor pattern.

By means of this configuration, the radiating element and the substratecan be integrally manufactured, and hence inexpensive manufacture can becarried out. Further, an attempt can also be made to achieve a morestable characteristic.

The antenna apparatus of the present invention includes the groundconductor that is formed on the first substrate from a conductorpattern.

By means of this configuration, the ground conductor and the substratecan be integrally manufactured, and hence inexpensive manufacture can becarried out. Further, an attempt can also be made to achieve a morestable characteristic.

The antenna apparatus of the present invention includes the radiatingelement and the ground conductor that are arranged such that an intervalbetween the radiating element and the second ground conductor becomesgreater than the thickness of the first substrate.

By means of this configuration, the distance between the radiatingelement and the ground conductor can be ensured. Hence, occurrence of adrop in the input impedance of the radiating element can be prevented,and matching with the feeding section can be readily achieved.

The antenna apparatus of the present invention includes the radiatingelement that is folded in a horizontal direction with respect to thefirst substrate.

By means of this configuration, the input impedance of the radiatingelement can be enhanced. Even when the input impedance has become loweras a result of the ground conductor having been placed in the vicinityof the poles of the radiating element, matching to the feeding sectioncan be effected readily.

In the antenna apparatus of the present invention, the radiating elementhas a dipole configuration having a structure folded in a verticaldirection with respect to the substrate, and the radiating elementcomprises a lower conductor placed on the first substrate, foldedsections placed on both ends of the lower conductor in an uprightposition with respect to the first substrate, and an upper conductordisposed for connecting ends of the folded ends.

By means of this configuration, the radiating element can be arranged ina three-dimensionally folded manner. Accordingly, the degree of designfreedom of the antenna is increased, and the area used for mounting theantenna can be reduced.

The antenna apparatus further comprises a second substrate provided onthe first substrate, wherein the lower conductor is interposed betweenthe first and second substrates, the folded section is provided so as topenetrate through the second substrate, and the upper substrate isprovided on the second substrate.

By means of this configuration, a radiating element having a foldedstructure can be formed by means of providing a substrate with amultilayer structure. Hence, the antenna apparatus can be manufacturedmore inexpensively, and the characteristic can be made more stable.

The antenna apparatus further comprises a dielectric block on the firstsubstrate, wherein the lower conductor, the folded section, and theupper conductor are provided on and/or in the dielectric block.

By means of this configuration, the radiating element and/or theparasitic element can be arranged in the dielectric block of a highdielectric material in a three-dimensionally-folded manner. Accordingly,the degree of design freedom of the antenna is increased, and the areaused for mounting the antenna can be made very small. Moreover, adielectric antenna having a directivity switching function can bemanufactured.

In the antenna apparatus of the present invention, the radiating elementcan be formed into a linear dipole.

According to this configuration, the radiating element can bemanufactured very simply.

In the antenna apparatus of the present invention, the radiating elementis formed into a dipole having the shape of a meander line.

By means of this configuration, the radiating element can be made verysmall.

In the antenna apparatus of the present invention, the first and secondswitches are formed from diode switches.

In the antenna apparatus of the present invention, the first and secondswitches are formed from FET switches.

In the antenna apparatus of the present invention, the first and secondswitches are formed from MEMS switches.

By means of these configurations, the switches can be realized in a verysimple configuration. Further, the switches can be made very compact byuse of the MEMS technique. Hence, an attempt can be made to miniaturizethe antenna.

A wireless terminal of the present invention comprises the antennaapparatus of the present invention; a transceiving section fortransceiving a radio wave by means of the antenna apparatus; an antennadirectivity switching section for switching directivity of the antennaapparatus; and a control section for controlling individual sections,wherein the control section controls the antenna directivity switchingsection and the transceiving section such that the antenna apparatus,whose directivity has been determined to exhibit superior receivingsensitivity on the basis of the intensity of a detected radio wave,performs transmission and receipt by causing the antenna directivityswitching section to switch directivity of the antenna apparatus andcausing the transceiving section to receive a radio wave.

In the wireless terminal of the present invention, the control sectionperforms control operation for causing the antenna apparatus to performdiversity receiving operation in a receiving state and causing theantenna apparatus, in a transmission state, to perform transmission withthe directivity used in a receiving state.

By means of this configuration, diversity receipt can be performed bymeans of switching the directivity of a single antenna even in amultipath environment. Hence, high-quality communication can be carriedout.

In the wireless terminal of the present invention, the control sectionperforms control operation for causing the antenna apparatus to performdiversity receiving operation in a receiving state and causing theantenna apparatus, in a transmission state, to perform transmission withdirectivity at which a maximum radiation direction of the antennaapparatus is oriented in a direction opposite a direction from thewireless terminal toward a user of the wireless terminal.

By means of this configuration, diversity receipt can be performed bymeans of switching the directivity of a single antenna even in amultipath environment. Hence, high-quality communication can be carriedout. Incidentally, during transmission, the directivity of the antennais not oriented toward the user who uses the wireless terminal.Accordingly, SAR can be enhanced.

ADVANTAGES OF THE INVENTION

According to the antenna apparatus of the present invention and thewireless terminal using the antenna apparatus, the directivity of theantenna can be switched between a backward direction and a zenithdirection by means of short-circuiting and opening switches. Even whenthe usage pattern of the wireless terminal changes as in the case ofvoice communication and data transmission, the directivity of theantenna is changed optimally for the usage pattern, whereby high-qualitycommunication can be carried out.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1( a) and (b) shows a schematic view of a directivity switchingantenna according to a first embodiment of the present invention.

FIGS. 2( a) and (b) shows the principle of operation for switchingdirectivity of the directivity switching antenna according to the firstembodiment of the present invention.

FIG. 3( a) is a cross-sectional profile of the directivity switchingantenna according to the first embodiment of the present inventionachieved when G=D; and (b) Directivity of the directivity switchingantenna according to the first embodiment of the present inventionacquired when the switch is switched at G=D.

FIG. 4( a) is a cross-sectional profile of the directivity switchingantenna according to the first embodiment of the present inventionachieved when G≦0; and (b) Directivity of the directivity switchingantenna according to the first embodiment of the present inventionacquired when the switch is short-circuited at G≦0.

FIG. 5( a) is a cross-sectional profile of the directivity switchingantenna according to the first embodiment of the present inventionachieved when G=D/4; and (b) Directivity of the directivity switchingantenna according to the first embodiment of the present inventionacquired when the switch is switched at G=D/4.

FIG. 6( a) is a cross-sectional profile of the directivity switchingantenna according to the first embodiment of the present inventionachieved when G=D/2; and (b) Directivity of the directivity switchingantenna according to the first embodiment of the present inventionacquired when the switch is switched at G=D/2.

FIG. 7( a) is a cross-sectional profile of the directivity switchingantenna according to the first embodiment of the present inventionachieved when G=3/4×D; and (b) Directivity of the directivity switchingantenna according to the first embodiment of the present inventionacquired when the switch is switched at G=3/4×D.

FIG. 8( a) is a cross-sectional profile of the directivity switchingantenna according to the first embodiment of the present inventionachieved when G=19/20×D; and (b) Directivity of the directivityswitching antenna according to the first embodiment of the presentinvention acquired when the switch is switched at G=19/20×D.

FIG. 9 is a maximum radiation direction switching angle acquired whenthe switch is switched at 0≦G<D in relation to the directivity switchingantenna according to the first embodiment of the present invention.

FIGS. 10( a) and (b) shows a view showing an example positionalrelationship between a wireless terminal and a user achieved duringvoice conversation.

FIGS. 11( a) and (b) shows a view showing an example positionalrelationship between a wireless terminal and a user achieved during datacommunication.

FIG. 12 is a view showing example radiation directivity characteristicsof the antenna acquired during voice conversation and datacommunication.

FIGS. 13( a) and (b) show a schematic view of a directivity switchingantenna according to a second embodiment of the present invention.

FIGS. 14( a) and (b) show a schematic view of a directivity switchingantenna according to the second embodiment of the present invention.

FIGS. 15( a) and (b) show a schematic view of a directivity switchingantenna according to a third embodiment of the present invention.

FIG. 16 is a view showing a relationship between switching operation ofa switch and directivity of an antenna, which pertains to the thirdembodiment of the present invention.

FIGS. 17( a) and (b) shows a schematic view showing a directivityswitching antenna according to a fourth embodiment of the presentinvention.

FIGS. 18( a) to (c) shows a view showing an example configuration of aradiating element having structures folded within an X-Y plane accordingto the fourth embodiment of the present invention.

FIGS. 19( a) and (b) shows a view showing an example configuration of aradiating element having structures folded within a Y−Z plane accordingto the fourth embodiment of the present invention.

FIGS. 20( a) and (b) shows a schematic view of the directivity switchingantenna using the radiating element having one of the folded structuresof the fourth embodiment of the present invention.

FIGS. 21( a) and (b) shows a schematic view of the directivity switchingantenna using a dielectric substrate of multilayer structure accordingto the fourth embodiment of the present invention.

FIGS. 22( a) and (b) shows a schematic view of a directivity switchingantenna using a dielectric block according to the fourth embodiment ofthe present invention.

FIG. 23 A schematic view of a wireless terminal according to a fifthembodiment of the present invention.

FIGS. 24( a) and (b) shows a schematic view of a directivity switchingantenna according to a sixth embodiment of the present invention.

FIG. 25 is the principle of operation for switching directivity of thedirectivity switching antenna according to the sixth embodiment of thepresent invention.

FIGS. 26( a) and (b) shows an example configuration of the directivityswitching antenna according to the sixth embodiment of the presentinvention.

FIG. 27( a) is the directivity of the directivity switching antenna ofthe sixth embodiment of the present invention achieved when the switchis switched; and (b) A view showing example directivity acquired whenthe length of a first metal conductor of the directivity switchingantenna according to the sixth embodiment of the present invention ischanged.

FIGS. 28( a) and (b) shows an example configuration of the directivityswitching antenna according to the sixth embodiment of the presentinvention.

FIG. 29( a) Directivity of the directivity switching antenna of thesixth embodiment of the present invention achieved when the switch isswitched; and (b) A view showing example directivity acquired when thelength of a first metal conductor of the directivity switching antennaaccording to the sixth embodiment of the present invention is changed.

FIGS. 30( a) and (b) shows a view showing an example positionalrelationship between a wireless terminal and a user acquired duringvoice conversation.

FIGS. 31( a) and (b) shows a view showing an example positionalrelationship between a wireless terminal and a user acquired during datacommunication.

FIG. 32 is a view showing example radiation directivity characteristicsof the antenna acquired during voice conversation and datacommunication.

FIGS. 33( a) and (b) shows an example configuration of the directivityswitching antenna according to the sixth embodiment of the presentinvention.

FIG. 34 is a schematic view of a directivity switching antenna accordingto a seventh embodiment of the present invention.

FIG. 35 is a directivity of switches disposed symmetrically with respectto the lengthwise direction of a radiating element in the directivityswitching antenna according to the seventh embodiment of the presentinvention.

FIGS. 36( a) and (b) shows the directivity of switches disposedasymmetrically with respect to the lengthwise direction of a radiatingelement in the directivity switching antenna according to the seventhembodiment of the present invention.

FIGS. 37( a) and (b) shows a schematic view of a directivity switchingantenna according to an eighth embodiment of the present invention.

FIG. 38 is a view showing a relationship between switching operation ofa switch and directivity of an antenna, which pertain to the eighthembodiment of the present invention.

FIGS. 39( a) and (b) shows a schematic view of a directivity switchingantenna according to a ninth embodiment of the present invention.

FIGS. 40( a) to (c) shows a view showing an example configuration of aradiating element having structures folded within an X-Y plane in thedirectivity switching antenna according to the ninth embodiment of thepresent invention.

FIGS. 41( a) and (b) shows a view showing an example configuration of aradiating element having structures folded within a Y−Z plane in thedirectivity switching antenna according to the ninth embodiment of thepresent invention.

FIGS. 42( a) and (b) shows a schematic view showing the directivityswitching antenna, according to the ninth embodiment of the presentinvention, which uses a radiating element having structures foldedwithin a Y−Z plane.

FIGS. 43( a) and (b) shows a schematic view of the directivity switchingantenna using a dielectric substrate of multilayer structure accordingto the ninth embodiment of the present invention.

FIGS. 44( a) and (b) shows a schematic view of the directivity switchingantenna using a dielectric block according to the ninth embodiment ofthe present invention.

FIG. 45 is a schematic view of a wireless terminal according to a tenthembodiment of the present invention.

FIG. 46 is a schematic view of a related-art directivity switchingantenna of Patent Document 1.

FIG. 47 is a schematic view of a related-art directivity switchingantenna of Patent Document 2.

FIG. 48 is a schematic view of a related-art directivity switchingantenna of Patent Document 3.

FIGS. 49( a) and (b) shows the directivity of the related-artdirectivity switching antenna of Patent Document 3.

FIG. 50 is a schematic view of a related-art directivity switchingantenna of Patent Document 4.

FIGS. 51( a) and (b) shows the directivity of the related-artdirectivity switching antenna of Patent Document 4.

DESCRIPTIONS OF THE REFERENCE NUMERALS

-   1 DIRECTIVITY SWITCHING ANTENNA-   2 DIELECTRIC SUBSTRATE-   3 RADIATING ELEMENT-   4 FEEDING POINT-   5 FIRST GROUND CONDUCTOR-   6 PARASITIC ELEMENT-   7 SWITCH-   8 SECOND GROUND CONDUCTOR-   9 END PORTION-   10 CONTROL CIRCUIT-   11 USER-   12 WIRELESS TERMINAL-   13 DISPLAY SECTION-   14 OPERATION SECTION-   15 AUXILIARY ELEMENT-   16 REFLECTOR-   17 PARASITIC ELEMENT-   18 SWITCH-   19 END PORTION-   20 RADIATING ELEMENT-   21 LOWER CONDUCTOR-   22 FOLDED SECTION-   23 UPPER CONDUCTOR-   24 DIELECTRIC SUBSTRATE-   25 DIELECTRIC BLOCK-   26 TRANSCEIVING SECTION-   27 CONTROL SECTION-   28 ANTENNA DIRECTIVITY SWITCHING SECTION-   29, 30 CONTROL SIGNALS-   101 PARASITIC ELEMENT-   102 FEEDING ELEMENT-   103 AUXILIARY ELEMENT-   104 CONTROL ELEMENT-   111 BOTTOM BOARD-   112 ANTENNA ELEMENT-   113 TO 116 PARASITIC ELEMENTS-   117 TO 120 DIELECTRIC SUBSTRATES-   201 DIRECTIVITY SWITCHING ANTENNA-   202 DIELECTRIC SUBSTRATE-   203 RADIATING ELEMENT-   204 FEEDING POINT-   205 GROUND CONDUCTOR-   206 FIRST METAL CONDUCTOR-   207 a, b SWITCHES-   208 END PORTION-   209 CONTROL CIRCUIT-   210 USER-   211 WIRELESS TERMINAL-   212 DISPLAY SECTION-   213 OPERATION SECTION-   214 CONDUCTOR PIECE-   215 DIODE SWITCH-   216 RADIATING ELEMENT-   217 LOWER CONDUCTOR-   218 FOLDED SECTION-   219 UPPER CONDUCTOR-   220 DIELECTRIC SUBSTRATE-   221 DIELECTRIC BLOCK-   222 TRANSCEIVING SECTION-   223 CONTROL SECTION-   224 ANTENNA DIRECTIVITY SWITCHING SECTION-   225, 226 CONTROL SIGNALS-   227 SECOND METAL CONDUCTOR-   301 ANTENNA ELEMENT-   302 MATCHING CIRCUIT-   303 RECEIVING CIRCUIT-   304 RECEIVING ELECTRIC FIELD INTENSITY COMPARATOR-   305 CONTROL CIRCUIT-   306, 307 EARTH METAL CONDUCTORS-   308 HIGH-FREQUENCY SWITCH-   311 ANTENNA-   312 ANTENNA ELEMENT-   313, 314 ANTENNA REFLECTORS-   315 MOLD

BEST MODES FOR IMPLEMENTING THE INVENTION

Antenna apparatuses of embodiments of the present invention and wirelessterminals using them will be described in detail hereunder by referenceto the drawings.

FIRST EMBODIMENT

FIG. 1 is a schematic view of a directivity switching antenna accordingto a first embodiment of the present invention. FIG. 1( a) is aperspective view, and FIG. 1( b) is a cross-sectional profile takenalong line A-A′ shown in FIG. 1( a).

A directivity switching antenna apparatus 1 comprises a dielectricsubstrate 2 of thickness “t”; a radiating element 3 which is formed froma linear conductor provided on the dielectric substrate 2 and has alength of L; a feeding point 4; a first ground conductor 5 provided onthe dielectric substrate 2 in plane with the radiating element 3; aparasitic element 6 of length Ld(<L) which is provided on the dielectricsubstrate in plane with the radiating element 3 and substantiallyparallel to the radiating element 3; switches 7 interposed between thefirst ground conductor 5 and the parasitic element 6; a second groundconductor 8 provided on a surface of the dielectric substrate 2 oppositeto the surface thereof where the radiating element 3 is provided; an endportion 9 of the second ground conductor 8; and a control circuit 10 forcontrolling a short-circuit and opening of the switches 7.

Descriptions will now be provided on the assumption that the radiatingelement 3, the first ground conductor 5, the parasitic element 6, andthe second ground conductor 8 are formed on the dielectric substrate 2from a conductor pattern. Forming these elements on the dielectricsubstrate 2 leads to the advantage of the ability to miniaturize theantenna apparatus by virtue of shortening a wavelength by means ofchanging a dielectric constant and the advantage of the antennaapparatus becoming inexpensive, easily mass-produced, and stable interms of an antenna characteristic.

Operation of the directivity switching antenna apparatus according tothe first embodiment of the present invention will now be described. Ahigh-frequency signal fed from the feeding point 4 is radiated in theair from the radiating element 3. In the present embodiment, theradiating element 3 is described as having the configuration of adipole. FIG. 2 shows the principle of directivity switching operation ofthe present invention. The directivity of the antenna becomesomnidirectional within a plane XZ as shown in (1) of FIG. 2( b) when aground conductor is not disposed around the radiating element 3 as shownin (1) of FIG. 2( a).

The first ground conductor 5 and the parasitic element 6 are provided inplane with the radiating element 3. The switches 7 are short-circuitedby means of a control signal output from the control circuit 10, to thusbring the first ground conductor 5 and the parasitic element 6 intoelectrical conduction with each other. Namely, the radiating element 3is enclosed by the ground conductor as shown in (2) of FIG. 2( a). Asshown in (2) of FIG. 2( b), the antenna exhibits directivity where themaximum radiation arises in directions ±Z. Further, when the switches 7are opened by the control signal output from the control circuit 10;namely, when a portion surrounding the radiating element 3 is separatedfrom the ground conductor as shown in (3) of FIG. 2( a), the parasiticelement 6 acts as a director. As shown in (3) of FIG. 2( b), the antennabecomes unidirectional and exhibits the maximum radiation in a direction+X. Namely, the directivity of the antenna can be switched through about90° by means of short-circuiting or opening the switches 7.

As shown in (2) of FIG. 2( a), according to the above configuration,however, when the switches 7 remain short-circuited, the antenna becomesbi-directional and exhibits the maximum radiation in directions ±Z. Whenonly the conductor pattern of (2) is placed on the dielectric substrate2 of the wireless terminal, a radiation field also arises in thedirection −Z toward the human body (i.e., the direction opposite theback), which in turn invokes deterioration of SAR. Accordingly, as shownin FIG. 1, the second ground conductor 8 is provided on the surface ofthe dielectric substrate 2 opposite the radiating element 3. In a statewhere the switches 7 remain short-circuited, a radiation field in thedirection −Z toward the human body is blocked, to thus realizeunidirectivity in the direction +Z. Influence of the arrangement of thesecond ground conductor 8 on switching of directivity of the antennawill be described in detail.

In FIG. 1( b), an interval between the radiating element 3 and theparasitic element 6 in the direction of the X axis is taken as D. Aninterval between the radiating element 3 and the end portion 9 of thesecond ground conductor 8 in the direction of the X axis is taken as G.At this time, as can be seen from the cross-sectional profile of thedirectivity switching antenna of the first embodiment of the presentinvention shown in FIG. 3( a), which is obtained at G=D, when theinterval G is made equal to or slightly longer than the interval D,substantially equal directivity is achieved when the switches 7 areshort-circuited or opened.

FIG. 3( b) shows directivity of the directivity switching antenna of thefirst embodiment of the present invention, which is achieved when theswitch is switched at G=D. By reference to FIG. 3( b), it is ascertainedthat the directivity of the antenna has not yet been switched bytoggling actions of the switches 7. This shows that, as a result of thesecond ground conductor 8 being provided beneath the parasitic element6, the parasitic element 6 does not operate as a director.

As in the case of the cross-sectional profile of the directivityswitching antenna apparatus of the first embodiment of the presentinvention shown in FIG. 4( a), which is acquired at G≦0, when theinterval G assumes a negative value, the second ground conductor 8 isnot present beneath the radiating element 3. Hence, in the state wherethe switches 7 remain short-circuited, an electromagnetic wave isintensely radiated in the direction −Z, as well. FIG. 4( b) is a viewshowing directivity of the directivity switching antenna of the firstembodiment of the present invention acquired when the switch isshort-circuited at G≦0, and showing directivity achieved when theswitches 7 are short-circuited when the interval G is −2 mm, −1 mm, and0 mm, respectively. From FIG. 4( b), when the interval G assumes a valueof −2 mm and a value of −1 mm, an electromagnetic wave havingsubstantially the same intensity as that of the electromagnetic waveemitted in the direction +Z is understood to be radiated in thedirection −Z, as well. When the interval G is 0 mm, the radiation fieldemitted in the direction −Z is understood to be suppressed by about 5 dBas compared with the radiation field emitted in the direction +Z.

As in the case of the cross-sectional profile of the directivityswitching antenna apparatus of the first embodiment of the presentinvention shown in FIG. 5( a), which is acquired at G=D/4, the endportion 9 of the second ground conductor 8 is arranged so as to comebetween the radiating element 3 and the parasitic element 6 in thedirection of the X axis; namely, the interval G satisfies the relationalexpression of 0≦G<D, thereby toggling the switches 7, to thus implementdesired directivity switching operation. By way of an example, FIG. 5(b) shows directivity acquired at a frequency F when the switches 7 areshort-circuited and opened, on condition that the radiating element 3having a length L=0.7λ is disposed on the dielectric substrate 2 havinga dielectric constant of 3.8 and a thickness “t” of 0.03λ; that theparasitic element 6 having a length of Ld=0.6λ is placed at a positionspaced from the radiating element 3 by a distance D=0.13λ; and that theinterval G between the radiating element 3 and the end portion 9 of thesecond ground conductor 8 in the direction of the X axis assumes D/4.From FIG. 5( b), the directivity of the antenna is understood to havebeen changed through about 90° by means of switching actions of theswitches 7.

In order to cause the parasitic element 6 to operate as a director, theinterval D between the radiating element 3 and the parasitic element 6is preferably increased to a value of about 0.25λ. However, the antennasize becomes greater as a result of the interval D being increased.Hence, directivity can be switched without increasing the interval D toa value of about 0.25λ, as in the case of the present embodiment. Thelength of the parasitic element 6 is adjusted so as to act as a directorwhen the switches 7 are opened. However, for instance, so long as theparasitic element 6 is configured so that its length can be varied,directivity can also be varied by means of adjusting a reactancecomponent of the director. A method for varying the length of theparasitic element 6 may comprise dividing the parasitic element 6 into aplurality of conductor pieces, placing the switches 7 among theconductor pieces, and varying the length of the parasitic element 6 bymeans of short-circuiting/opening the switches 7, or may comprise addinga variable capacity element, such as a varactor diode, to the parasiticelement 6 to thus electrically adjust the length of the parasiticelement in accordance with a control voltage.

Although FIG. 5( b) shows directivity achieved when the switch isswitched at interval G=D/4, FIGS. 6 to 8 show another example where theinterval G has fulfilled the relational expression of 0≦G<D. FIG. 6( a)is a cross-sectional profile of the directivity switching antennaaccording to the first embodiment of the present invention achieved whenG=D/2, and (b) shows directivity of the directivity switching antennaaccording to the first embodiment of the present invention acquired whenthe switch is switched at G=D/2. FIG. 7( a) is a cross-sectional profileof the directivity switching antenna according to the first embodimentof the present invention achieved when G=3/4×D, and (b) showsdirectivity of the directivity switching antenna according to the firstembodiment of the present invention acquired when the switch is switchedat G=3/4×D. FIG. 8( a) is a cross-sectional profile of the directivityswitching antenna according to the first embodiment of the presentinvention achieved when G=19/20×D, and (b) shows directivity of thedirectivity switching antenna according to the first embodiment of thepresent invention acquired when the switch is switched at G=19/20×D.Numerical values other than the interval G shown in FIGS. 6 through 8are common to those employed in FIG. 5( a). From FIGS. 6( b), 7(b), and8(b), it can be ascertained that directivity is switched through about90° by means of toggling actions of the switches 7.

FIG. 9 shows a directivity switching angle achieved by the directivityswitching antenna apparatus according to the first embodiment of thepresent invention when the switch is switched in a range of −D/2<G<D.The horizontal axis represents a G/D ratio, and the vertical axisrepresents a directivity switching angle showing a switching angle atwhich the maximum radiation direction is acquired during switching ofthe switch. As shown in FIGS. 5 through 8, FIG. 9 shows that thedirectivity switching angel is in the vicinity of about 90° when G/Dvaries from 0 to 1 and that directivity can be switched so long as G/Dvaries from 0 to 1. Meanwhile, it is also ascertained that, as G/Dapproaches 1, the directivity of the antenna is not switched even whenthe switches 7 have been toggled. This shows that, as the second groundconductor 8 is placed so as to approach the lower portion of theparasitic element 6, the parasitic element 6 becomes inoperative as adirector. Moreover, even when G/D is in the vicinity of 0, thedirectivity switching angle is in the vicinity of 90°. At this time, asindicated by the directivity achieved when the switch has beenshort-circuited at G=0 mm shown in FIG. 4( b), the radiation field issuppressed when compared with the radiation field in the direction +Z.However, the radiation field is also emitted in the direction −Z, aswell. Therefore, setting the interval G within a range of 0<G<D, excepta range where the interval comes to 0 or D, is preferable. The drawingshows that, when no consideration is given to emission of the radiationfield in the direction −Z, directivity can be switched by means ofsetting the interval within a range of −D/4<G<D.

A positional relationship between the user and the wireless terminalachieved during voice conversation and during data communication willnow be described in detail. FIG. 10 shows an example positionalrelationship between the wireless terminal and the user achieved duringvoice conversation. FIG. 11 show an example positional relationshipbetween the wireless terminal and the user achieved during datacommunication. When voice conversation is performed, a positionalrelationship such as that shown in FIG. 10 is assumed to exist betweenthe user 11 and the wireless terminal 12. When data communication isperformed, a positional relationship such as that shown in FIG. 11 isassumed to exist between the user 11 and the wireless terminal 12.

During voice conversation, the user 11 uses the wireless terminal 12while placing it adjacent to the side of the user's head. During datacommunication, the user 11 commonly performs operation by use of theoperation section 14 while ascertaining messages appearing on thedisplay section 13 of the wireless terminal 12. Therefore, as shown inFIG. 12, during voice conversation, directivity of the antenna providedin the wireless terminal 12 is preferably switched such that the maximumradiation direction achieved by the directivity of the antenna isoriented toward the back of the wireless terminal 12 (i.e., a directionopposite the display surface of the display section 13). Further,directivity is preferably switched such that, during data communication,the maximum radiation direction achieved by the directivity of theantenna comes to the zenith direction of the wireless terminal 12 (i.e.,the horizontal direction with respect to the display surface of thedisplay section 13 and an upper direction with displayed messages).

Since the wireless terminal 12 has such a directivity switchingfunction, the radiation field originating from the antenna is notoriented toward the user 11, which in turn results in improvement in SARand expectations for improved antenna gains. Consequently, thedirectivity switching antenna 1 is placed in the wireless terminal 12such that the zenith direction in FIG. 12 is allocated to the directionX and such that the backward direction is allocated to the direction Z,whereby desired directivity characteristics can be attained during voiceconversation and data communication.

As above, the first ground conductor 5 and the parasitic element 6 areprovided around the radiating element 3 placed on the dielectricsubstrate 2 as well as in plane with the same. The switches 7 areinterposed between the first ground conductor and the parasitic element6. The second ground conductor 8 is provided below the radiating element3 with the dielectric substrate 2 sandwiched therebetween. In such astructure, the end portion 9 of the second ground conductor 8 is placedbetween the radiating element 3 and the parasitic element 6. Further,the switches 7 are toggled by use of the control circuit 10, therebyswitching the directivity of the antenna through about 90°. Therefore,there is yielded an advantage of the ability to realize an antennaapparatus which switches directivity according to a usage pattern of awireless terminal.

Further, a wireless terminal is configured by use of the directivityswitching antenna described in connection with the embodiment. As aresult, the directivity of the antenna is switched according to theusage pattern of the wireless terminal, to thus enhance performance ofthe wireless terminal. Therefore, a highly-reliable wirelesscommunications system can be provided.

The present embodiment has described that the radiating element 3 isformed from the conductor pattern on the dielectric substrate 2.However, the radiating element 3 may also be formed from a linearconductor, such as a wire, or by means of sheeting.

The present embodiment has described that the radiating element 3 isformed into a linear dipole. However, the radiating element 3 is notlimited to the linear dipole but may also be formed into, e.g., ameander line.

The present embodiment has described that the radiating element 3, thefirst ground conductor 5, the parasitic element 6, and the second groundconductor 8 are assumed to be formed on the dielectric substrate 2.However, use of the dielectric substrate is not always required. Forinstance, the radiating element 3, the parasitic element 6, the groundconductors 5, 8, and the like, are formed by means of sheeting, and theconstituent elements may be fixed by means of a foaming agent.

The present embodiment has described that the second ground conductor 8is formed from a conductor pattern on the side of the dielectricsubstrate 2 opposite the surface thereof where the radiating element 3is formed. For instance, the second ground conductor may be provided noton the dielectric substrate 2 but on an enclosure of the wirelessterminal 12 that is spaced from the dielectric substrate 2 by a givendistance. By means of such a configuration, there is yielded theadvantage of the ability to broadly ensure an interval between theradiating element 3 and the second ground conductor 8 and to easilyeffect matching of the antenna.

The present embodiment has not described particularly the configurationof the switches 7. However, a diode switch, an FET switch, a MEMSswitch, or the like, can be used.

SECOND EMBODIMENT

FIG. 13 is a schematic view of a directivity switching antenna accordingto a second embodiment of the present invention. FIG. 13( a) is aperspective view, and FIG. 13( b) is a cross-sectional profile takenalong line A-A′ shown in FIG. 13( a). In FIG. 13, the directivityswitching antenna apparatus includes auxiliary elements 15. In otherrespects, the second embodiment is identical with the first embodiment,and hence its explanation is omitted.

Operation of the directivity switching antenna apparatus according tothe second embodiment of the present invention will now be described.The basic operation of the antenna apparatus is identical with thatdescribed in connection with the first embodiment, and hence itsexplanation is omitted. The auxiliary elements 15 are provided at bothends of the parasitic element 6, and the switches 7 are interposedbetween the parasitic element 6 and the auxiliary elements 15. Inrelation to the auxiliary element 15, a total length of the parasiticelement 6 and the auxiliary element 15 acquired when the switches 7 areshort-circuited is set such that the parasitic element 6 acts as areflector with respect to the radiating element 3. By means of such aconfiguration, when the switches 7 have been opened, the parasiticelement 6 acts as a director, and directivity is oriented in thedirection +X. When the switches 7 have been short-circuited, theparasitic element 6 acts as a reflector, and directivity is oriented inthe direction +Z. Therefore, the advantage acquired when thesurroundings of the radiating element 3 are covered with a groundconductor is yielded.

As above, the auxiliary elements 15 are disposed at both ends of theparasitic element 6. The switches 7 are toggled by use of the controlcircuit 10 to thus switch the parasitic element 6 between the directorand the reflector, whereby the directivity of the antenna can beswitched through about 90°. Hence, there is yielded the advantage of theability to realize an antenna apparatus which switches directivityaccording to a usage pattern.

Moreover, a wireless terminal is configured by use of the directivityswitching antenna apparatus described in connection with the presentembodiment. Hence, the directivity of the antenna is switched accordingto the usage pattern, to thus enhance the performance of the wirelessterminal. Thus, a highly-reliable wireless communications system can beprovided.

The present embodiment has described that the radiating element 3 isformed from a conductor pattern on the dielectric substrate 2. However,the radiating element 3 may also be formed from a linear conductor, suchas a wire, or by means of sheeting.

The present embodiment has described that the radiating element 3 isformed into a linear dipole. However, the radiating element 3 is notlimited to the linear dipole but may also be formed into, e.g., ameander line.

The present embodiment has described that the first ground conductor 5is placed in the direction −X of the radiating element 3. As shown inFIG. 14, the same advantage is yielded even when the a reflector 16 isused in place of the first ground conductor 5.

The present embodiment has described that the radiating element 3, thefirst ground conductor 5, the parasitic element 6, the second groundconductor 8, and the auxiliary elements 15 are assumed to be formed onthe dielectric substrate 2. However, use of the dielectric substrate isnot always required. For instance, the radiating element 3, theparasitic element 6, the ground conductors 5, 8, the auxiliary elements15, and the like, may be formed by means of sheeting, and theconstituent elements fixed by means of a foaming agent.

The present embodiment has described that the second ground conductor 8is formed from a conductor pattern on the side of the dielectricsubstrate 2 opposite the surface thereof where the radiating element 3is formed. For instance, the second ground conductor may be provided noton the dielectric substrate 2 but on an enclosure of the wirelessterminal 12 that is spaced from the dielectric substrate 2 by a givendistance. By means of such a configuration, there is yielded theadvantage of the ability to broadly ensure an interval between theradiating element 3 and the second ground conductor 8 and to easilyeffect matching of the antenna.

The present embodiment has not described the particular configuration ofthe switches 7. However, a diode switch, an FET switch, a MEMS switch,or the like, can be used.

THIRD EMBODIMENT

FIG. 15 is a schematic view of a directivity switching antenna accordingto a third embodiment of the present invention. FIG. 15( a) is aperspective view, and FIG. 15( b) is a cross-sectional profile takenalong line A-A′ shown in FIG. 15( a). In FIG. 15, the directivityswitching antenna apparatus 1 comprises the auxiliary elements 15, aparasitic element 17, switches 18, and the end portion 19 on the part ofthe second ground conductor 8 facing the parasitic element 17. In otherrespects, the present embodiment is identical with the first embodiment,and hence its explanation is omitted.

Operation of the directivity switching antenna apparatus 1 according tothe third embodiment of the present invention will now be described. Thebasic operation of the antenna apparatus is identical with thatdescribed in connection with the first embodiment, and hence itsexplanation is omitted. The auxiliary elements 15 are provided at bothends of the parasitic element 6, and the switches 7 are interposedbetween the parasitic element 6 and the auxiliary elements 15. Inrelation to the auxiliary element 15, a total length of the parasiticelement 6 and the auxiliary elements 15 acquired when the switches 7 areshort-circuited is set such that the parasitic element 6 acts as areflector with respect to the radiating element 3.

In place of the first ground conductor 5, the parasitic element 17,which is equal in length to the parasitic element 6, is provided. Theauxiliary elements 15 are provided at both ends of the parasitic element17, as well. The switches 18 are interposed between the parasiticelement 17 and the auxiliary elements 15. An interval between theradiating element 3 and the parasitic element 17 is made equal to theinterval D between the radiating element 3 and the parasitic element 6.Moreover, the interval G between the radiating element 3 and the endportion 19 on the part of the second ground conductor 8, facing theparasitic element 17, in the direction of the +X axis is also made equalto the interval G between the radiating element 3 and the end portion 9on the part of the second ground conductor 8, facing the parasiticelement 6, in the direction of the +X axis. Specifically, a symmetricalstructure is obtained within the YZ plane including the radiatingelement 3.

At this time, the switches 7, 18 are controlled by use of the controlcircuit 10, to thus switch directivity. Detailed descriptions will beprovided in this respect. FIG. 16 shows a relationship betweenshort-circuiting/opening actions of the switches 7, 18 and directivityof the antenna. When the switches 7, 18 have been short-circuited, theparasitic elements 6, 17 operate as reflectors. Hence, the directivityof the antenna is oriented to the direction +Z in FIG. 11.

Next, when the switch 7 is short-circuited and the switch 18 is opened,the parasitic element 6 operates as a reflector, and the parasiticelement 17 operates as a director. Hence, the directivity of the antennais oriented in the direction −X shown in FIG. 15. Next, the switch 7 isopened to thus short-circuit the switch 18, so that the parasiticelement 6 operates as a director, and the parasitic element 17 operatesas a reflector. Accordingly, the directivity of the antenna is orientedin the direction +X in FIG. 15. When both the switches 7, 18 are opened,the parasitic elements 6, 17 operate as directors. In relation to thedirectivity of the antenna, the maximum radiation direction is in thedirection +Z. However, a substantially omnidirectional characteristic isobtained.

As mentioned above, the auxiliary elements 15 are provided at both endsof each of the parasitic elements 6, 17. Further, the parasitic elements6, 17 are controlled by the control circuit 10 such that, by means ofswitching actions of the switches 7, 18, the parasitic element 6 isswitched to the director and the parasitic element 17 is switched to thereflector, whereby the directivity of the antenna can be switched atintervals of 90° in the direction ±X and the direction ±Z. There isyielded the advantage of the ability to embody an antenna apparatuswhich, according to the usage pattern of the wireless terminal, selectsthe direction ±X opposite the direction toward the user even when thewireless terminal is disposed such that the radiation direction istoward the user during, e.g., data communication, thereby switchingdirectivity.

By means of configuring a wireless terminal by use of the directivityswitching antenna described in the embodiment, the performance of thewireless terminal can be enhanced by means of switching the directivityof the antenna according to a usage pattern. Thus, a highly-reliablewireless communications system can be provided.

The present embodiment has described that the radiating element 3 isformed from a conductor pattern on the dielectric substrate 2. However,the radiating element 3 may also be formed from a linear conductor, suchas a wire, or by means of sheeting.

The present embodiment has described that the radiating element 3 isformed into a linear dipole. However, the radiating element 3 is notlimited to the linear dipole but may also be formed into, e.g., ameander line.

The present embodiment has described that the radiating element 3, theparasitic elements 6 and 17, the second ground conductor 8, and theauxiliary elements 19 are assumed to be formed on the dielectricsubstrate 2. However, use of the dielectric substrate is not alwaysrequired. For instance, the radiating element 3, the parasitic elements6 and 17, the ground conductor 8, the auxiliary elements 19, and thelike, may be formed by means of sheeting, and the constituent elementsfixed by means of a foaming agent.

The present embodiment has described that the second ground conductor 8is formed from a conductor pattern on the side of the dielectricsubstrate 2 opposite the surface thereof where the radiating element 3is formed. For instance, the second ground conductor may be provided noton the dielectric substrate 2 but on an enclosure of the wirelessterminal 12 that is spaced a given distance from the dielectricsubstrate 2. By means of such a configuration, there is yielded theadvantage of the ability to broadly ensure an interval between theradiating element 3 and the second ground conductor 8 and to easilyeffect matching of the antenna.

The present embodiment has not described the particular configuration ofthe switches 7. However, a diode switch, an FET switch, a MEMS switch,or the like, can be used.

FOURTH EMBODIMENT

FIG. 17 is a schematic view of a directivity switching antenna accordingto a fourth embodiment of the present invention. FIG. 17( a) is aperspective view, and FIG. 17( b) is a cross-sectional profile takenalong line A-A′ shown in FIG. 17( a). In FIG. 17, the directivityswitching antenna apparatus 1 comprises a radiating element 20 having afolded structure. In other respects, the present embodiment is identicalwith the first embodiment, and hence its explanation is omitted.

Operation of the directivity switching antenna apparatus according tothe fourth embodiment of the present invention will now be described.For instance, in FIG. 1, the radiating element 3 and the second groundconductor 8 are separated from each other by the thickness “t” of thedielectric substrate 2; namely, 0.008λ. When the ground conductor 8 isplaced in the vicinity of the pole of the radiating element 3 asmentioned above, input impedance of the radiating element 3 becomesdrastically smaller than in the case where the ground conductor 8 is notprovided in the vicinity of the poles of the radiating element 3.

By means of providing the radiating element 3 with a folded structure asin the case of the radiating element 20, the input impedance of theradiating element can be increased. For instance, the input impedance ofa double-folded dipole antenna shown in FIG. 18( b) is quadruple theinput impedance of a common dipole antenna shown in FIG. 18( a). Theinput impedance of a triple-folded dipole antenna shown in FIG. 18( c)is eight times the input impedance of the common dipole antenna. As aresult of use of the radiating element 20 having a folded structure asshown in FIG. 17, input impedance of the antenna acquired at the feedingpoint 4 can be increased, which facilitates matching of the antenna witha 50Ω-based microstrip line or coaxial line.

As above, the radiating element 20 is provided with a folded structure,and the switches 7 are toggled by use of the control circuit 10. As aresult, there is yielded the advantage of the ability to realize anantenna apparatus which increases input impedance of the antenna, tothus facilitate matching while switching the directivity of the antennathrough about 90° and which switches directivity according to a usagepattern of the wireless terminal.

Moreover, the wireless terminal is configured by use of the directivityswitching antenna apparatus described in connection with the presentembodiment. Hence, the directivity of the antenna is switched accordingto the usage pattern, to thus enhance the performance of the wirelessterminal. Thus, a highly-reliable wireless communications system can beprovided.

The present embodiment has described that the radiating element 20 isformed from a conductor pattern on the dielectric substrate 2. However,the radiating element 20 may also be formed from a linear conductor,such as a wire, or by means of sheeting.

The present embodiment has described that the radiating element 20 isformed into a linear dipole. However, the radiating element 20 is notlimited to the linear dipole and may also be formed into, e.g., ameander line.

The present embodiment has described that the radiating element 20, thefirst ground conductor 5, the parasitic element 6, and the second groundconductor 8 are assumed to be formed on the dielectric substrate 2.However, use of the dielectric substrate is not always required. Forinstance, the radiating element 20, the parasitic element 6, the groundconductors 5, 8, and the like, may be formed by means of sheeting, andthe constituent elements fixed by means of a foaming agent.

The present embodiment has described that the second ground conductor 8is formed from a conductor pattern on the side of the dielectricsubstrate 2 opposite the surface thereof where the radiating element 20is formed. For instance, the second ground conductor may be provided noton the dielectric substrate 2 but on an enclosure of the wirelessterminal 12 that is spaced a given distance from the dielectricsubstrate 2. By means of such a configuration, there is yielded theadvantage of the ability to broadly ensure an interval between theradiating element 20 and the second ground conductor 8 and to easilyeffect matching of the antenna.

In the present embodiment, the radiating element 3, 20 is formed into atwo-dimensional structure within the XY plane. However, the radiatingelement 20 is not limited to this structure. As shown in, e.g., FIGS.19( a) and (b), the radiating element 3, 20 may be formed into astructure where ends of the radiating element are folded. By means ofsuch a folded structure, the antenna length can be shortened, and theantenna can be miniaturized.

A method for manufacturing an antenna folded within a YZ plane as shownin FIGS. 19( a), (b) will now be described. As shown in FIG. 20, amethod for manufacturing an antenna in the simplest manner is tomanufacture an antenna by sheeting. A lower conductor 21, a foldedsection 22, and an upper conductor 23, all of which constitute aradiating element, may be integrally formed by means of sheeting.Alternatively, the lower conductor 21 may have been formed beforehand onthe dielectric substrate 2 from a conductor pattern, and only the foldedsection 22 and the upper conductor 23 may be formed by means ofsheeting.

In addition to sheeting, as shown in FIG. 21, another manufacturingmethod may also be adopted; for instance, newly placing a dielectricsubstrate 24 on the dielectric substrate 2; forming the lower conductor21 from a planer conductor pattern sandwiched between the dielectricsubstrates 2, 24; forming the upper conductor 23 from the conductorpattern on a surface of the dielectric substrate 24 opposite the surfacethereof that faces the dielectric substrate 2; forming the foldedsection 22 from a through hole, or the like, passing through thedielectric substrate 24; and electrically connecting the lower conductor21 to the upper conductor 23.

By means of adoption of such a configuration, the directivity switchingantenna apparatus can be manufactured from a multilayer substrate. Asshown in FIG. 22, each of the lower conductor 21, the folded section 22,and the upper conductor 23 may be formed from a pattern on a dielectricblock 25 made of a highly-dielectric material such as ceramic or thelike. By means of the configuration, the antenna apparatus can beminiaturized to a great extent. Further, the parasitic element 6 and theground conductor 5 are formed from a pattern on the dielectric block 25,whereby a dielectric antenna having a directivity switching function canbe manufactured.

FIFTH EMBODIMENT

FIG. 23 is a schematic view of a wireless terminal of a fifth embodimentof the present invention. In FIG. 23, the wireless terminal 12 comprisesa transceiving section 26 set to a frequency range where datacommunication and voice conversation are carried out, a control section27, and an antenna directivity switching section 28.

Operation of the wireless terminal according to the present embodimentof the present invention will now be described. For instance, when thewireless terminal is used indoors, a multipath environment is presumedto arise for reasons of obstacles such as walls. Under suchcircumstances, the antenna can address the multipath environment bymeans of diversity receiving operation. Common diversity receivingoperation is achieved by means of placing a plurality of antennas in aspatially-separated manner. However, use of the plurality of antennasresults in an increase in the area required to mount the antenna, aswell as a necessity for an area required to mount an antenna switch,because the antenna switch is used for selecting any one of theplurality of antennas.

By use of the directivity switching antennas 1 described in connectionwith the first through fourth embodiments, directional diversityreceiving can be effected while the area required to mount the antennais maintained to that required to mount a single antenna. Detaileddescriptions are given in this regard.

In FIG. 23, the wireless terminal 12 is formed from the directivityswitching antenna 1, the transceiving section 26, the control section27, and the antenna directivity switching section 28. With such aconfiguration, during receiving operation, the high-frequency signalreceived by the directivity switching antenna 1 is subjected tofrequency conversion and demodulation in the transceiving section 26,and the thus-converted demodulated signal is transmitted to the controlsection 27. At this time, the control section 27 monitors received powergained as a result of the directivity of the directivity switchingantenna 1 having been switched, and a control signal 29 is sent to theantenna directivity switching section 28 such that the directivity ofthe antenna, at which the greatest received power is attained, isacquired. On the basis of the control signal 29 output from the controlsection 27, the antenna directivity switching section 28 determinesdirectivity at which superior receiving sensitivity is achieved; andtransmits a control signal 30 in order to switch the directivity of thedirectivity switching antenna 1 such that superior receiving sensitivityis achieved. By means of the control signal 30, the directivityswitching antenna 1 is switched so as to acquire desired directivity. Inthe meantime, during transmission operation, the signal transmitted fromthe control section 27 is subjected to modulation and frequencyconversion at the transceiving section 26, and the thus-modulatedconverted signal is transmitted from the directivity switching antenna1. At this time, the directivity selected during receiving operation isused as the directivity of the directivity switching antenna 1.

As above, the wireless terminal is formed from the directivity switchingantenna 1, the transceiving section 26, the control section 27, and theantenna directivity switching section 28. Diversity receiving can beperformed by a single antenna, and therefore there is yielded theadvantage of the ability to implement a compact, high-performancewireless terminal.

The present embodiment has described that, during transmissionoperation, the directivity switching antenna 1 is used at the samedirectivity as that employed during receiving operation. However, thepresent invention is not limited to this embodiment. During receivingoperation, diversity receiving is performed by use of the directivityswitching antenna 1. During transmission, the radiation fieldoriginating from the directivity switching antenna may be set so as notto propagate toward the user 11 who uses the wireless terminal 12. Forexample, there may be adopted a configuration of: fixing the directionalmaximum emission direction of the directivity switching antenna 1 in thebackward direction of the wireless terminal 12 during transmission; andfixing, at the time of transmission, the directional maximum emissiondirection of the directivity switching antenna 1 in the zenith directionof the wireless terminal 12 during data communication.

The present embodiment has described the wireless terminal 12 using thedirectivity switching antennas 1 described in connection with the firstthrough fourth embodiments. However, the present invention is notlimited to the embodiments. An antenna apparatus of any configurationmay be used, so long as the directivity of the antenna can be switchedbetween the zenith direction (i.e., the horizontal direction withrespect to the display surface of the display section 13 and the upwarddirection with reference to displayed messages) and the backwarddirection (the direction opposite the display surface of the displaysection 13) with respect to the wireless terminal 12 through about 90°.

SIXTH EMBODIMENT

FIG. 24 is a schematic view of a directivity switching antenna accordingto a sixth embodiment of the present invention. FIG. 24( a) is aperspective view, and FIG. 24( b) is a cross-sectional profile takenalong line A-A′ shown in FIG. 24( a). In FIG. 24, a directivityswitching antenna apparatus comprises a directivity switching antenna201; a dielectric substrate 202 of thickness “t”; a radiating element203 which is formed from a linear conductor provided on the dielectricsubstrate 202 and has a length of L; a feeding point 204; a groundconductor 205 provided on a surface of the dielectric substrate 202opposite the surface thereof on which the radiating element 203 isprovided; a first metal conductor 206 which is provided on thedielectric substrate 202 in plane with the ground conductor 205 and inparallel to the radiating element 203 and which is electricallyinsulated from the ground conductor 205 and has a length Lm and a widthWm; switches 207 a interposed between the ground conductor 205 and thefirst metal conductor 206; an end portion 208 on the part of the groundconductor 205 facing the first metal conductor 206; and a controlcircuit 209 for controlling short-circuit and opening of the switches207 a.

Descriptions will now be provided on the assumption that the radiatingelement 203, the ground conductor 205, and the first metal conductor 206are formed on the dielectric substrate 202 from a conductor pattern.Forming these elements on the dielectric substrate 202 leads to theadvantage of the ability to miniaturize the antenna apparatus by virtueof shortening a wavelength by means of a dielectric constant and theadvantage of the antenna apparatus becoming inexpensive, easilymass-produced, and stable in terms of an antenna characteristic.

Operation of the directivity switching antenna apparatus according tothe sixth embodiment of the present invention will now be described. Ahigh-frequency signal fed from the feeding point 204 is radiated in theair from the radiating element 203. In the present embodiment, theradiating element 203 is described as having the configuration of adipole. FIG. 25 shows the principle of directivity switching operationof the present invention.

As shown in (1) of FIG. 25( a), when the ground conductor 205 is presentbeneath the radiating element 203, the directivity of the antennabecomes unidirectional and exhibits the maximum radiation direction inthe direction +Z direction as shown in (1) of FIG. 25( b). Next, asshown in (2) of FIG. 25( b), when the ground conductor 205 is notpresent in an area in the direction +X with reference to the radiatingelement 203, the antenna becomes unidirectional and exhibits the maximumradiation direction in the direction +X. As shown in (3) of FIG. 25( a),even when the first metal conductor 206 is arranged in the direction +Xwith respect to the radiating element 203 while being electricallyisolated from the ground conductor 205, the directivity of the antennabecomes unidirectional and exhibits the maximum radiation direction inthe direction +X by means of appropriately adjusting the length Lm andthe width Wm of the first metal conductor 206, substantially in the samemanner as in the case of (2) of FIG. 25( b).

When the ground conductor 205 and the first metal conductor 206 areconnected together by means of switches 207 a and the switches 207 a areshort-circuited, the first metal conductor 206 operates as the groundconductor 205, to thus exhibit directivity where the maximum radiationdirection appears in the direction +Z as in the case of (1) of FIG. 25(b). Further, when the switches 207 a are opened, the first metalconductor 206 operates as a director with regard to the radiatingelement 203. As shown in (3) of FIG. 25( b), the antenna exhibitsdirectivity where the maximum radiation direction appears in thedirection +X. Therefore, the directivity of the antenna can be switchedthrough about 90° by means of switching actions of the switches 207 a.In order to switch the directivity of the antenna, the size of theground conductor 205, the size of the first metal conductor 206, arelative positional relationship between the radiating element 203 andthe ground conductor 205, and a relative positional relationship betweenthe radiating element 203 and the first metal conductor 206 becomeimportant. Detailed descriptions are given in this regard.

As can be seen from an example configuration of the directivityswitching antenna according to the sixth embodiment of the presentinvention shown in FIG. 26, the length of the radiating element 203 isassumed to be L; the length of the first metal conductor 206 in thedirection Y is assumed to be Lm; the width of the same in the directionX is assumed to be Wm; an interval between the radiating element 203 andthe end portion 208 on the part of the ground conductor 205, facing thefirst metal conductor 206, in the direction X is assumed to be D (thedirection +X is positive); and an interval between the ground conductor205 and the first metal conductor 206 is assumed to be sw. At this time,operation of the antenna apparatus varies between the case where theinterval D between the radiating element 203 and the end portion 208 onthe part of the ground conductor 205, facing the first metal conductor206, in the direction X is positive or negative. Each of the cases willnow be described.

First, consideration is given to the case where the interval D ispositive. As shown in FIG. 26, the ground conductor 205 is presentbeneath the radiating element 203. Hence, when switches 207 a areshort-circuited to thus activate the first metal conductor 206 as aground conductor, the antenna becomes unidirectional to thus exhibit, inunmodified form, the maximum radiation direction in the direction +Z. Inthe meantime, in order to orient the maximum radiation direction of theantenna in the direction +X when the switches 207 a are opened to thusdisconnect the first metal conductor 206 from the ground conductor, Lmis set such that the first metal conductor 206 operates as a directorwith respect to the radiating element 203

FIG. 27 shows directivity of the directivity switching antenna of thesixth embodiment of the present invention. FIG. 27( a) is a view showingdirectivity acquired when the switches 207 a are toggled with theradiating element 203 of L=16.5 mm (0.54λ) being provided on thedielectric substrate 202 having a dielectric constant of 3.8 and athickness t=0.5 mm (0.02λ); the interval D being 2 mm (0.06λ); thelength Lm of the first metal conductor 206 being 19 mm (0.62λ); thewidth Wm of the same being 2 mm (0.06λ); and the interval sw between theground conductor 205 and the first metal conductor 206 being 1 mm(0.03λ).

Further, FIG. 27( b) is a view showing directivity acquired when theswitches 207 a are opened with the length Lm of the first metalconductor 206, among the above parameters, being set to 13 mm (0.42λ)and 21 mm (0.68λ). From FIG. 27( a), when the length Lm of the firstmetal conductor 206 is 19 mm, the directivity of the antenna is switchedthrough about 90° by means of switching action of the switches 207 a. Itis understood that directivity can be switched by the first metalconductor 206 set to a length at which the first metal conductor acts asa director. When the length Lm of the first metal conductor 206 is setto 13 mm and 21 mm as shown in FIG. 27( b), the maximum radiationdirection of the antenna can be ascertained not to face the direction +Xduring opening of the switches 207 a.

Specifically, when the length Lm of the first metal conductor 206 is 13mm, the length is too short to cause the first metal conductor tosufficiently operate as a director.

Conversely, when the length Lm of the first metal conductor 206 is 21mm, the first metal conductor 206 is understood to act as a reflectorand suppress radiation in the direction +X. This shows that, when thefirst metal conductor 206 is used as a director, the length thereof mustbe set so as to fall within a range from about 0.42λ to 0.68λ.

Next, consideration is given to the case where the interval D isnegative. As indicated by an example configuration of the directivityswitching antenna according to the sixth embodiment of the presentinvention shown in FIG. 28, the ground conductor 205 is not presentbeneath the radiating element 203. In order to orient the maximumradiation direction to the direction +Z when the switches 207 a areshort-circuited, there must be adopted a configuration where the firstmetal conductor 206 is present beneath the radiating element 203.Namely, the sum of the interval sw between the ground conductor 205 andthe first metal conductor 206 and the width Wm of the first metalconductor 206 is made greater than the interval D, whereby the firstmetal conductor 206 can be disposed beneath the radiating element 203.

FIG. 29 shows directivity of the directivity switching antenna of thesixth embodiment of the present invention. FIG. 29( a) is a view showingdirectivity acquired when the switches 207 a are toggled with theradiating element 203 of L=16.5 mm (0.54λ) being provided on thedielectric substrate 202 having a dielectric constant of 3.8 and athickness t=0.5 mm (0.02λ); the interval D being −2 mm (−0.06λ); thelength Lm of the first metal conductor 206 being 19 mm (0.62λ); thewidth Wm of the same being 4 mm (0.12λ); and the interval sw between theground conductor 205 and the first metal conductor 206 being 1 mm(0.03λ). Further, FIG. 29( b) is a view showing directivity acquiredwhen the switches are short-circuited with the length Lm of the firstmetal conductor 206, among the parameters, being set to 10 mm (0.32λ)which is shorter than the length L of the radiating element 203.

From FIG. 29( a), when the length Lm of the first metal conductor 206 is19 mm, the directivity of the antenna is understood to have beenswitched through about 90° by means of switching actions of the switches207 a. In the meantime, as shown in FIG. 29( b), when the length Lm ofthe first metal conductor 206 is 10 mm, which is shorter than theradiating element 203, the maximum radiation direction of the antennacan be ascertained not to face the direction +Z during theshort-circuiting of the switches 207 a. Specifically, when the length Lmof the first metal conductor 206 is shorter than the length L of theradiating element 203, the first metal conductor 206 is understood notto sufficiently operate as a ground conductor during theshort-circuiting of the switches 207 a. Consequently, the length Lm ofthe first metal conductor 206 is preferably longer than the length L ofthe radiating element 203.

A positional relationship between the user and the wireless terminalachieved during voice conversation and data communication will now bedescribed in detail. FIG. 30 shows an example positional relationshipbetween the wireless terminal and the user achieved during voiceconversation. FIG. 31 shows an example positional relationship betweenthe wireless terminal and the user achieved during data communication.When voice conversation is performed, a positional relationship such asthat shown in FIG. 30 is assumed to exist between a user 210 and awireless terminal 211. When data communication is performed, apositional relationship such as that shown in FIG. 31 is assumed toexist between the user 210 and the wireless terminal 211.

During voice conversation, the user 210 uses the wireless terminal 211while placing it adjacent to the side of the user's head. During datacommunication, the user 210 commonly performs operation by use of anoperation section 213 while ascertaining messages appearing on a displaysection 212 of the wireless terminal 211. Therefore, as shown in FIG.32, during voice conversation, directivity of the antenna provided inthe wireless terminal 211 is preferably switched such that the maximumradiation direction achieved by the directivity of the antenna isoriented toward the back of the wireless terminal 211 (i.e., a directionopposite the display surface of the display section 212). Directivity isalso preferably switched such that, during data communication, themaximum radiation direction achieved by the directivity of the antennacomes to the zenith direction of the wireless terminal 211 (i.e., thehorizontal direction with respect to the display surface of the displaysection 212 and an upper direction with displayed messages).

Since the wireless terminal 211 has such a directivity switchingfunction, the radiation field originating from the antenna is notoriented toward the user 210, which in turn results in improvement inSAR and expectations for improved antenna gains. Consequently, adirectivity switching antenna 201 is placed in the wireless terminal 212such that the zenith direction in FIG. 32 is allocated to the directionX and such that the backward direction is allocated to the direction Z,whereby desired directivity characteristics can be attained during voiceconversation and data communication.

As above, the directivity switching antenna comprises the radiatingelement 203 provided on the dielectric substrate 202; the groundconductor 205 disposed on a surface of the dielectric substrate 202opposite the surface thereof on which the radiating element 203 isprovided; the first metal conductor which is provided on the dielectricsubstrate 202 in plane with the ground conductor 205 and in parallel tothe radiating element 203 and is electrically insulated from the groundconductor 205; and the switches 207 a interposed between the groundconductor 205 and the first metal conductor 206. The switches 207 a areswitched between the short-circuit position and the open position by useof the control circuit 209, so that the directivity of the antenna canbe switched through about 90°. There is yielded the advantage of theability to implement an antenna whose directivity is switched accordingto a usage pattern of the wireless terminal.

Further, a wireless terminal is configured by use of the directivityswitching antenna described in connection with the embodiment. As aresult, the directivity of the antenna is switched according to theusage pattern of the wireless terminal, to thus enhance performance ofthe wireless terminal. Therefore, a highly-reliable wirelesscommunications system can be provided.

The present embodiment has described that the radiating element 203 isformed from the conductor pattern on the dielectric substrate 202.However, the radiating element 203 may also be formed from a linearconductor, such as a wire, or by means of sheeting.

The present embodiment has described that the radiating element 203 isformed into a linear dipole. However, the radiating element 203 is notlimited to the linear dipole and may also be formed into, e.g., ameander line.

The present embodiment has described that the radiating element 203, theground conductor 205, and the first metal conductor 206 are assumed tobe formed on the dielectric substrate 202. However, use of thedielectric substrate 202 is not always required. For instance, theradiating element 203, the ground conductor 205, and the first metalconductor 206 may be formed by means of sheeting, and the constituentelements may be fixed by means of a foaming agent.

The length of the first metal conductor 206 is set to a length at whichthe first metal conductor operates as a director when the switches 207 aare opened. However, for instance, so long as there is adopted aconfiguration where the length of the first metal conductor 206 can bechanged, directivity can also be changed by means of adjusting areactance component of the director.

The method for changing the length of the first metal conductor 206 mayinclude dividing the first metal conductor 206, in the lengthwisedirection thereof, into a plurality of conductor pieces; placing theswitches 207 a among the respective conductor pieces; andshort-circuiting/opening the switches 207 a to thus change the lengthsof the conductor pieces. Alternatively, the method may include adding avariable capacitance element, such as a varactor diode, to the firstmetal conductor 206, and electrically adjusting the length of the firstmetal conductor 206 in accordance with the control voltage.

In the present embodiment, the ground conductor 205 and the first metalconductor 206 are formed from a conductor pattern on the side of thedielectric substrate 202 opposite the surface thereof on which theradiating element 203 is provided. However, for instance, the groundconductor 205 and the first metal conductor 206 may be provided not onthe dielectric substrate 202 but on the enclosure of the wirelessterminal 211 spaced a given distance from the dielectric substrate 202.By adoption of such a configuration, the interval between the radiatingelement 203 and the ground conductor 205 can be broadly ensured, andthere is yielded the advantage of the ability to facilitate matching ofthe antenna when the ground conductor 205 is present beneath theradiating element 203.

By utilization of the fact that a change arises in directivity duringshort-circuiting of the switches 207 a by means of changing the width Wmof the first metal conductor 206, the directivity switching angle of theantenna, which has been switched by means of short-circuiting andopening of the switches 207 a, can be adjusted. For instance, asillustrated by the example configuration of the directivity switchingantenna according to the sixth embodiment of the present invention shownin FIG. 33, there may be adopted a configuration of dividing the firstmetal conductor 206 into a plurality of conductor pieces 214 withrespect to the direction of the X axis and connecting the conductorpieces together by means of the switches 207 a.

SEVENTH EMBODIMENT

FIG. 34 is a schematic view of a directivity switching antenna accordingto a seventh embodiment of the present invention. In FIG. 34, thedirectivity switching antenna includes diode switches 215. The remainderof the configuration is identical with that of the sixth embodiment, andhence its explanation is omitted.

Operation of the directivity switching antenna according to the seventhembodiment of the present invention will be described hereinbelow. Sincethe basic operation of the antenna is the same as that described inconnection with the sixth embodiment, its explanations are omitted. Asshown in FIG. 34, the ground conductor 205 and the first metal conductor206 are connected at a plurality of locations by means of the diodeswitches 215.

By means of such a configuration, when the diode switches 215 areshort-circuited, the first metal conductor 206 operates as the groundconductor 205, and directivity of the antenna is oriented in thedirection +Z. When the diode switches 215 are opened, the first metalconductor 206 operates as a director with respect to the radiatingelement 203, and the directivity of the antenna is oriented in thedirection +X. The directivity of the antenna can be changed throughabout 90° by means of switching actions of the diode switches 215.However, at this time, the directivity characteristic is affected by thepositions where the diode switches 215 are mounted. Detaileddescriptions are given in this regard.

Consideration is given to a case where the two diode switches 215 aremounted while being displaced from the feeding point 204 in therespective directions ±Y by d1, d2. FIG. 35 is a view showing that, oncondition that the radiating element 203 of L=16.5 mm (0.54λ) isprovided on the dielectric substrate 202 having a dielectric constant of3.8 and a thickness t=0.5 mm (0.02λ); the first metal conductor 206 hasa length Lm=19 mm (0.62λ) and a width Wm=4 mm (0.12λ); and the intervalsw between the ground conductor 205 and the first metal conductor 206 is1 mm (0.03λ) and that mount positions of the diode switches 215 are setto d1=d2=d and “d” is changed, directivity acquired when the diodeswitches 215 are short-circuited.

In FIG. 35, ref shows a state where the ground conductor 205 and thefirst metal conductor 206 are in complete electrical connection witheach other in an ideal manner. When d=2 mm, directivity is not orientedin the direction +Z. Even when the diode switches 215 areshort-circuited, the first metal conductor 206 is understood not tooperate as the ground conductor 205. However, when “d” is increased tod=7 mm where the mount positions of the diode switches 215 comesubstantially to locations beneath the respective ends of the radiatingelement 203, directivity becomes substantially equivalent to ref. It canbe ascertained that a unidirectional characteristic exhibiting themaximum radiation direction in the direction +Z has been acquired.

Both ends of the radiating element 203 are located at an area where thehighest electrical potential is achieved. By means of electricallyconnecting the ground conductor 205 to the first metal conductor 206 inthe vicinity of this area, there is achieved a state substantiallyequivalent to an ideal, complete electrical connection. Hence, the mountpositions of the diode switches 205 are desirably set to locations belowthe high electrical potential area of the radiating element 203.

As above, the two diode switches 215 are interposed between the groundconductor 205 and the first metal conductor 206, and the mount positionsof the diode switches 215 are set in the vicinity of the high potentialarea of the radiating element 203, whereby the directivity of theantenna can be switched through about 90° by means of short-circuitingand opening the switches. Accordingly, there is yielded an advantage ofthe ability to implement an antenna whose directivity is switchedaccording to the usage pattern of the wireless terminal.

Moreover, as a result of the wireless terminal being constituted by useof the directivity switching antenna described in connection with thepresent embodiment, the wireless terminal is configured by use of thedirectivity switching antenna described in connection with theembodiment. Directivity of the antenna is switched according to a usagepattern of the wireless terminal, whereby the performance of thewireless terminal can be enhanced. There can be provided ahighly-reliable wireless communications system.

The present embodiment has described that the radiating element 203 isformed from the conductor pattern on the dielectric substrate 202.However, the radiating element 203 may also be formed from a linearconductor, such as a wire, or by means of sheeting.

The present embodiment has described that the radiating element 203 isformed into a linear dipole. However, the radiating element 203 is notlimited to the linear dipole but may also be formed into, e.g., ameander line.

The present embodiment has described that the radiating element 203, theground conductor 205, and the first metal conductor 206 are assumed tobe formed on the dielectric substrate 202. However, use of thedielectric substrate is not always required. For instance, the radiatingelement 203, the ground conductor 205, the first metal conductor 206,and the like, may be formed by means of sheeting, and the constituentelements fixed by means of a foaming agent.

The present embodiment has described that the ground conductor 205 isformed from a conductor pattern on the side of the dielectric substrate202 opposite the surface thereof where the radiating element 203 isformed. For instance, the ground conductor 205 may be provided on anenclosure of the wireless terminal 211 that is spaced from thedielectric substrate 202 by a given distance. By means of such aconfiguration, there is yielded the advantage of the ability to broadlyensure an interval between the radiating element 203 and the groundconductor 205 and to easily effect matching of the antenna when theground conductor 205 is present beneath the radiating element 203.

In the present embodiment, the diode switches 215 are used as switchingelements. However, the switching elements are not limited to the diodeswitches. Other switches, such as FET switches or switches using theMEMS technique, or other switching circuits may alternatively be used.

The present embodiment has described a case where the two diode switches215 are arranged so as to become symmetrical about the lengthwisedirection of the radiating element 203, but d1 and d2 may be arranged indifferent lengths. FIG. 36( a) shows directivities acquired within theplane XY when d2 is set to 2 mm and 7 mm, respectively, on conditionthat d1 is equal to 2 mm.

As can be seen from FIG. 36( a), directivity within the plane XY can beadjusted by means of changing the distance between d1 and d2. Further,even when one of the diode switches 215 is short-circuited and the otheris opened, directivity within the plane XY can be adjusted. FIG. 36( b)is a view showing directivity within the plane XY acquired when d1=d2=7mm is set in FIG. 34; when one of the diode switches 215 isshort-circuited; and when the other diode switch is opened. From FIG.36( b), it is understood that one of the diode switches 215 is opened,whereby the electromagnetic field becomes asymmetrical with respect tothe lengthwise direction of the radiating element 203; and that themaximum radiating direction of directivity is displaced from thedirection of the X axis within the plane XY. Directivity can bethree-dimensionally adjusted by utilization of these facts.

The present embodiment has described the case where the two diodeswitches 215 are used. However, the number of diode switches is notnecessarily limited to two. Needless to say, there may be adopted aconfiguration where two or more diode switches are interposed betweenthe ground conductor 205 and the first metal conductor 206. Directivitywithin the plane XY can be controlled more accurately by means ofincreasing the number of switches.

By means of changing the width Wm of the first metal conductor 206, thedirectivity switching angle of the antenna, which is acquired when thediode switches 215 are switched by means of short-circuiting or opening,can be adjusted. For instance, there may be adopted a configurationwhere the first metal conductor 206 is divided into a plurality ofconductor pieces 214 with respect to the direction of the X axis and theconductor pieces are connected together by means of switches 207 a.

EIGHTH EMBODIMENT

FIG. 37 is a schematic view of a directivity switching antenna accordingto an eighth embodiment of the present invention. FIG. 37( a) is aperspective view, and FIG. 37( b) is a cross-sectional profile takenalong line A-A′ shown in FIG. 37( a). In FIG. 37, a second metalconductor 227 is placed in plane with the ground conductor 205 on thedielectric substrate 202. The second metal conductor 227 is formed so asto assume a length Lm and a width Wm and to be electrically insulatedfrom the ground conductor 205 such that the second metal conductor isplaced in parallel to the radiating element 203 and symmetrical with thefirst metal conductor 206 with respect to the Y axis. The second metalconductor 227 includes switches 207 b which are interposed between thesecond metal conductor 227 and the end portion 228 of the groundconductor 205 facing the second metal conductor 227. In other respects,the present embodiment is identical with the sixth embodiment, and henceits explanation is omitted here for brevity.

Operation of the directivity switching antenna apparatus according tothe eighth embodiment of the present invention will be describedhereunder. Since the basic operation is the same as that described inconnection with the first embodiment, its explanation is omitted. Thesecond metal conductor 227 is arranged, with respect to the groundconductor 205 and symmetrically to the first metal conductor withrespect to the Y axis.

At this time, the switches 207 a, 207 b are controlled by use of thecontrol circuit 209, to thus switch directivity. Detailed descriptionsare given in this regard.

FIG. 38 shows a relationship between operation for short-circuiting andopening the switches 207 a, 207 b and the directivity of the antenna.When both the switches 207 a, 207 b are short-circuited, the first metalconductor 206 and the second metal conductor 227 constitute a portion ofthe ground conductor 205. Hence, the directivity of the antenna isoriented in the direction +Z in FIG. 37. Next, when the switch 207 b isshort-circuited and the switch 207 a is opened, the first metalconductor 206 acts as a director, and the second metal conductor 227operates as a part of the ground conductor 205. Accordingly, thedirectivity of the antenna is oriented in the direction +X in FIG. 37.

When the switch 207 a is short-circuited and the switch 207 b is opened,the first metal conductor 206 constitutes a part of the ground conductor205, and the second metal conductor 227 operates as a director. Hence,the directivity of the antenna is oriented in the direction −X shown inFIG. 37. When both the switches 207 a, 207 b are opened, the metalconductors 206, 227 operate as directors. However, a substantiallyomnidirectional characteristic is acquired as the directivity of theantenna.

As above, the second metal conductor 227 is provided symmetrical withthe first metal conductor 206 with respect to the Y axis. The firstmetal conductor 206 and the second metal conductor 227 are controlled byuse of the control circuit 209 such that the metal conductors areswitched between the director and the ground conductor by means ofswitching actions of the switches 207 a, 207 b. Thereby, the directivityof the antenna can be switched at intervals of 90° in the directions ±Xand the direction +Z. Hence, there is yielded the advantage of theability to implement an antenna apparatus which switches directivity bymeans of selecting the direction ±X opposite the direction toward theuser even when, e.g., the wireless terminal is arranged such that theradiation direction is oriented to the user according to the usagepattern of the wireless terminal during data communication.

Further, so long as the antenna of such a configuration is provided on acar, directivity can be switched back and forth even when the directionof the car has changed. Hence, there is yielded the advantage of theability to receive a terrestrial digital broadcast.

Moreover, the wireless terminal is configured by use of the directivityswitching antenna described in connection with the embodiment, so thatthe performance of the wireless terminal can be enhanced by means ofswitching the directivity of the antenna according to the usage patternof the wireless terminal. A highly-reliable wireless communicationssystem can be provided.

The present embodiment has described that the radiating element 203 isformed from the conductor pattern on the dielectric substrate 202.However, the radiating element 3 may also be formed from a linearconductor, such as a wire, or by means of sheeting.

The present embodiment has described that the radiating element 203 isformed into a linear dipole. However, the radiating element 203 is notlimited to the linear dipole but may also be formed into, e.g., ameander line.

The present embodiment has described that the radiating element 203, theground conductor 205, the first metal conductor 206, and the secondmetal conductor 227 are assumed to be formed on the dielectric substrate202. However, use of the dielectric substrate is not always required.For instance, the radiating element 203, the ground conductor 205, thefirst metal conductor 206, the second metal conductor 227, and the like,may be formed by means of sheeting, and the constituent elements fixedby means of a foaming agent.

The present embodiment has described that the ground conductor 205 isformed from a conductor pattern on the side of the dielectric substrate202 opposite the surface thereof where the radiating element 203 isformed. For instance, the ground conductor 205 may be provided on anenclosure of the wireless terminal 211 that is spaced from thedielectric substrate 202 by a given distance. By means of such aconfiguration, there is yielded the advantage of the ability to broadlyensure an interval between the radiating element 203 and the groundconductor 205 and to easily effect matching of the antenna when theground conductor 205 is present beneath the radiating element 203.

In the present embodiment, the diode switches 215 are used as switchingelements. However, the switching elements are not limited to the diodeswitches. Other switches, such as FET switches or switches using theMEMS technique, or other switching circuits may also be used.

The first metal conductor 206 and the second metal conductor 227 are setto a length at which the first and second metal conductors operate as adirector when the switches 207 a, 207 b are opened. However, forinstance, so long as there is adopted a configuration where the lengthof the first metal conductor 206 and that of the second metal conductor227 can be changed, directivity can also be changed by means ofadjusting a reactance component of the director.

The method for changing the length of the first metal conductor 206 andthe length of the second metal conductor 227 may include dividing thefirst and second metal conductors 206 and 227, in the lengthwisedirection thereof, into a plurality of conductor pieces; placing theswitches 207 a, 207 b among the respective plurality of conductorpieces; and short-circuiting/opening the switches 207 a, 207 b to thuschange the lengths of the conductor pieces. Alternatively, the methodmay include adding a variable capacitance element, such as a varactordiode, to the first and second metal conductors 206, 227, andelectrically adjusting the lengths of the first and second metalconductors 206, 207 in accordance with the control voltage.

By utilization of the phenomenon of directivity achieved at the time ofshort-circuiting of the switches 207 a, 207 b being changed by means ofchanging the width Wm of the first and second metal conductors 206, 227,the directivity switching angle of the antenna, which has been acquiredby means of toggling the switches 207 a, 207 b through short-circuitingand opening operations, can be adjusted.

NINTH EMBODIMENT

FIG. 39 is a schematic view of a directivity switching antenna accordingto a ninth embodiment of the present invention. FIG. 39( a) is aperspective view, and FIG. 39( b) is a cross-sectional profile takenalong line A-A′ shown in FIG. 39( a). In FIG. 39, the directivityswitching antenna includes a radiating element 216 having a foldedstructure. In other respects, the present embodiment is identical withthe sixth embodiment, and hence its explanation is omitted here forbrevity.

Operation of the directivity switching antenna apparatus according tothe ninth embodiment of the present invention will now be described. Forinstance, in FIG. 24, the dielectric substrate 202 having a thickness of“t”=0.016λ is interposed between the radiating element 203 and theground conductor 205 such that the radiating element 203 and the groundconductor 205 are separated from each other by the amount correspondingto a thickness “t”=0.016λ. Thus, when the ground conductor 205 is placedin the vicinity of the radiating element 203, the input impedance of theradiating element 203 has become drastically smaller than that achievedin a state where the ground conductor 205 is not provided.

When the radiating element 203 is configured to have such a foldedstructure as that of the radiating element 216, the input impedance ofthe radiating element can be increased. For instance, the inputimpedance of a double folded dipole such as that shown in FIG. 40( b)becomes quadruple the input impedance of a common dipole antenna shownin FIG. 40( a). The input impedance of a triple-folded dipole antennashown in FIG. 40( c) becomes eight times the input impedance of thecommon dipole antenna. As a result of use of the radiating element 216having a folded structure as shown in FIG. 39, input impedance of theantenna acquired at the feeding point 204 can be increased, therebyfacilitating matching of the antenna with a 50Ω-based microstrip line orcoaxial line.

As above, the radiating element 216 is provided with a folded structure,and the switches 207 a are toggled by use of the control circuit 209. Asa result, there is yielded the advantage of the ability to realize anantenna apparatus which increases input impedance of the antenna to thusfacilitate matching while switching the directivity of the antennathrough about 90° and which switches directivity according to a usagepattern of the wireless terminal.

Moreover, a wireless terminal is configured by use of the directivityswitching antenna apparatus described in connection with the presentembodiment. Hence, the directivity of the antenna is switched accordingto the usage pattern of the wireless terminal, to thus enhance theperformance of the wireless terminal. Thus, a highly-reliable wirelesscommunications system can be provided.

The present embodiment has described that the radiating element 216 isformed from a conductor pattern on the dielectric substrate 202.However, the radiating element 216 may also be formed from a linearconductor, such as a wire, or by means of sheeting.

The present embodiment has described that the radiating element 216 isformed into a linear dipole. However, the radiating element 216 is notlimited to the linear dipole but may also be formed into, e.g., ameander line.

The present embodiment has described that the radiating element 216, theground conductor 205, and the first metal conductor 206, are assumed tobe formed on the dielectric substrate 202. However, use of thedielectric substrate is not always required. For instance, the radiatingelement 216, the ground conductor 205, the first metal conductor 206,and the like, may be formed by means of sheeting, and the constituentelements fixed by means of a foaming agent.

In the present embodiment, the ground conductor 205 is formed from aconductor pattern on the side of the dielectric substrate 202 oppositethe surface thereof where the radiating element 216 is formed. Forinstance, the ground conductor 205 may be provided not on the dielectricsubstrate 202 but on an enclosure of the wireless terminal 211 that isspaced from the dielectric substrate 202 by a given distance. By meansof such a configuration, there is yielded the advantage of the abilityto broadly ensure an interval between the radiating element 216 and theground conductor 205 and to easily effect matching of the antenna.

In the present embodiment, the radiating elements 203 216 are formedinto a two-dimensional structure within the XY plane. However, theradiating elements 203, 216 are not limited to this structure. As shownin, e.g., FIGS. 41( a), (b), the radiating element 203, 216 may beformed into a structure where ends of the radiating elements 203, 216are folded. By means of such a folded structure, the antenna length canbe shortened, and the antenna can be miniaturized.

A method for manufacturing an antenna folded within a YZ plane as shownin FIGS. 41( a), (b) will now be described. As shown in FIG. 42, amethod for manufacturing an antenna in the simplest manner is tomanufacture an antenna by sheeting. At this time, a lower conductor 217,a folded section 218, and an upper conductor 219, all of whichconstitute a radiating element, may be integrally formed by means ofsheeting. Alternatively, the lower conductor 217 may have been formedbeforehand on the dielectric substrate 202 from a conductor pattern, andonly the folded section 218 and the upper conductor 219 formed by meansof sheeting.

In addition to sheeting, as shown in FIG. 43, another manufacturingmethod may also be adopted; for instance, placing a second dielectricsubstrate 220 on the dielectric substrate 202; forming the lowerconductor 217 from a planer conductor pattern sandwiched between thedielectric substrates 202, 220; forming the upper conductor 219 from theconductor pattern on a surface of the second dielectric substrate 220opposite the surface thereof that faces the dielectric substrate 202;forming the folded section 218 from a through hole, or the like, passingthrough the second dielectric substrate 220; and electrically connectingthe lower conductor 217 to the upper conductor 219.

By means of adoption of such a configuration, the directivity switchingantenna apparatus can be manufactured through use of a multilayersubstrate. As shown in FIG. 44, each of the lower conductor 217, thefolded section 218, and the upper conductor 219 may be formed from apattern on a dielectric block 221 made of a highly-dielectric materialsuch as ceramic or the like. By means of the configuration, the antennaapparatus can be miniaturized to a great extent.

TENTH EMBODIMENT

FIG. 45 is a diagrammatic representation of a wireless terminalaccording to a tenth embodiment of the present invention. In FIG. 45,the wireless terminal comprises a transceiving section 222 set tofrequency bands used for data communication and voice conversation; acontrol section 223; and an antenna directivity switching section 224.

Operation of the wireless terminal according to the tenth embodiment ofthe present invention will now be described. For instance, when thewireless terminal is used indoors, a multipath environment is presumedto arise for reasons of obstacles such as walls. Under suchcircumstances, the antenna can address the multipath environment bymeans of diversity receiving operation. Common diversity receivingoperation is achieved by means of placing a plurality of antennas in aspatially-separated manner. However, use of the plurality of antennasresults in an increase in the area required to mount the antenna, aswell as a necessity for an area required to mount an antenna switch,because the antenna switch is used for selecting any one of theplurality of antennas.

By use of the directivity switching antennas described in connectionwith the sixth through ninth embodiments, directional diversityreceiving can be effected while the area required to mount the antennais maintained to that required to mount a single antenna. Detaileddescriptions are given in this regard.

In FIG. 45, the wireless terminal 211 is formed from the directivityswitching antenna 201, the transceiving section 222, the control section223, and the antenna directivity switching section 224. With such aconfiguration, during receiving operation, the high-frequency signalreceived by the directivity switching antenna 201 is subjected tofrequency conversion and demodulation in the transceiving section 222,and the thus-converted demodulated signal is transmitted to the controlsection 223. At this time, the control section 223 monitors receivedpower gained as a result of the directivity of the directivity switchingantenna 201 having been switched, and a control signal 225 is sent tothe antenna directivity switching section 224 such that the directivityof the antenna, at which the greatest received pattern is attained, isacquired.

On the basis of the control signal 225 output from the control section223, the antenna directivity switching section 224 determinesdirectivity at which superior receiving sensitivity is achieved; andtransmits a control signal 226 in order to switch the directivity of thedirectivity switching antenna 201 such that superior receivingsensitivity is achieved. By means of the control signal 226, thedirectivity switching antenna 201 is switched so as to acquire desireddirectivity. In the meantime, during transmission operation, the signaltransmitted from the control section 223 is subjected to modulation andfrequency conversion at the transceiving section 222, and thethus-modulated converted signal is transmitted from the directivityswitching antenna 201. At this time, the directivity selected duringreceiving operation is used as the directivity of the directivityswitching antenna 201.

As above, the wireless terminal is formed from the directivity switchingantenna 201, the transceiving section 222, the control section 223, andthe antenna directivity switching section 224. Diversity receiving canbe performed by a single antenna, and therefore there is yielded theadvantage of the ability to implement a compact, high-performancewireless terminal.

The present embodiment has described that, during transmissionoperation, the directivity switching antenna 201 is used at the samedirectivity as that employed during receiving operation. However, thepresent invention is not limited to this embodiment. During receivingoperation, diversity receiving is performed by use of the directivityswitching antenna 201. During transmission, the radiation fieldoriginating from the directivity switching antenna may be set so as notto propagate toward the user 210 who uses the wireless terminal 211. Forexample, there may be adopted a configuration of: fixing the directionalmaximum emission direction of the directivity switching antenna 201 inthe backward direction of the wireless terminal 211 during voiceconversation; and fixing, at the time of transmission, the directionalmaximum emission direction of the directivity switching antenna 201 inthe zenith direction of the wireless terminal 211 during datacommunication.

The present embodiment has described the wireless terminal 211 using thedirectivity switching antennas 201 described in connection with thesixth through ninth embodiments. However, the present invention is notlimited to the embodiments.

An antenna apparatus of any configuration may be used, so long as thedirectivity of the antenna can be switched between the zenith direction(i.e., the horizontal direction with respect to the display surface ofthe display section 212 and the upward direction with reference todisplayed messages) and the backward direction (the direction oppositethe display surface of the display section 212) through about 90°.

The present invention has been described in detail by reference to thespecific embodiments. However, it is obvious to those skilled in the artthat the present invention can be subjected to various alterations ormodifications without departing from the spirit and scope of the presentinvention.

The present invention claims priority to Japanese Patent Application(No. 2004-290063) filed on Oct. 1, 2004 and Japanese Patent Application(No. 2004-290143) filed on Oct. 1, 2004, which are incorporated hereinby reference in their entireties.

INDUSTRIAL APPLICABILITY

The antenna apparatus of the present invention and the wireless terminalusing the antenna apparatus yield the advantage of the ability to switchthe directivity of the antenna between the backward direction and thezenith direction by means of short-circuiting and opening the switches.The antenna apparatus is useful as an antenna which enables high-qualitycommunication when applied to a wireless terminal to be employed invarious usage patterns such as voice conversation and datacommunication. Further, the present invention is also useful for usewith an information terminal, such as a wireless terminal or a PC, whichrequires diversity receiving operation.

The antenna apparatus of the present invention and the terminal usingthe antenna apparatus yield the advantage of the ability to switch thedirectivity of the antenna in three directions by means ofshort-circuiting and opening the switches. The antenna apparatus isuseful as an antenna which enables high-quality communication even inthe case of receipt of a terrestrial digital broadcast for avehicle-mounted device.

1. An antenna apparatus comprising: a linear radiating element placed ona first plane; a first parasitic element placed on the first plane inparallel to the radiating element; a first ground conductor placed onthe first plane; a first switch which connects both ends of the firstparasitic element to the first ground conductor; a second groundconductor placed on a second plane opposing the first plane; and acontrol unit which controls short-circuiting/opening of the switch,wherein a part of the first ground conductor is placed in parallel tothe radiating element and on a side opposite the first parasitic elementwith the radiating element sandwiched therebetween, and wherein thesecond ground conductor is placed opposite the radiating element, andends of the second ground conductor oppose an area sandwiched betweenthe radiating element and the first parasitic element.
 2. An antennaapparatus comprising: a linear radiating element placed on a firstplane; a first linear parasitic element placed on the first plane inparallel to the radiating element; a linear auxiliary element providedat both ends of the first parasitic element; a first ground conductorplaced on the first plane; a first switch which connects both ends ofthe first parasitic element to the auxiliary element; a second groundconductor placed on a second plane opposing the first plane; and acontrol unit which controls short-circuiting/opening of the switch,wherein the first ground conductor is placed in parallel to theradiating element and on a side opposite the first parasitic elementwith the radiating element sandwiched therebetween, and wherein thesecond ground conductor is placed opposite the radiating element, andends of the second ground conductor oppose an area sandwiched betweenthe radiating element and the first parasitic element.
 3. An antennaapparatus comprising: a linear radiating element placed on a firstplane; a first parasitic element placed on the first plane in parallelto the radiating element; a second linear parasitic element which isprovided on the first plane opposite the first parasitic element withthe radiating element interposed therebetween, and in parallel to theradiating element; a linear auxiliary element provided at both ends ofthe respective first and second parasitic elements; a first switch and asecond switch which connect both ends of the first and second parasiticelements to the auxiliary elements provided on both sides of therespective first and second parasitic elements; a second groundconductor placed on a second plane opposing the first plane; and acontrol unit which controls short-circuiting/opening of the switch,wherein the second ground conductor is placed opposite the radiatingelement, and one end of the second ground conductor opposes an areasandwiched between the radiating element and the first parasiticelement, and the other end of the second ground conductor opposes anarea sandwiched between the radiating element and the second parasiticelement.
 4. The antenna apparatus according to claim 3, furthercomprising a first substrate on which the first and second planes areprovided.
 5. The antenna apparatus according to claim 4, wherein theradiating element and the second ground conductor are arranged such thata spacing between the radiating element and the second ground conductorbecomes greater than the thickness of the first substrate.
 6. Theantenna apparatus according to claim 4, wherein the radiating elementhas a dipole configuration having a structure folded in a verticaldirection with respect to the substrate, and wherein the radiatingelement comprises: a lower conductor placed on the first substrate;folded sections placed on both ends of the lower conductor in an uprightposition with respect to the first substrate; and an upper conductordisposed for connecting ends of the folded ends.
 7. The antennaapparatus according to claim 6, further comprising: a second substrateprovided on the first substrate, wherein the lower conductor isinterposed between the first and second substrates, wherein the foldedsection is provided so as to penetrate through the second substrate, andwherein the upper conductor is provided on the second substrate.
 8. Theantenna apparatus according to claim 6, further comprising: a dielectricblock on the first substrate, wherein the lower conductor, the foldedsection, and the upper conductor are provided on and/or in thedielectric block.
 9. The antenna apparatus according to claim 3, whereinthe parasitic element becomes a director with respect to the radiatingelement when the switch is opened.
 10. The antenna apparatus accordingto claim 3, wherein the parasitic element and the auxiliary element actas reflectors with respect to the radiating element when the switchesare short-circuited.
 11. The antenna apparatus according to claim 3,wherein reactance of the parasitic element is variable.
 12. A wirelessterminal comprising: the antenna apparatus according to claim 3; atransceiving section for transceiving a radio wave by means of theantenna apparatus; an antenna directivity switching section forswitching directivity of the antenna apparatus; and a control sectionfor controlling individual sections, wherein the control sectioncontrols the antenna directivity switching section and the transceivingsection such that the antenna apparatus, whose directivity has beendetermined to exhibit superior receiving sensitivity on the basis of theintensity of a detected radio wave, performs transmission and receipt bycausing the antenna directivity switching section to switch directivityof the antenna apparatus and causing the transceiving section to receivea radio wave.
 13. The wireless terminal according to claim 12, whereinthe control section performs control operation for causing the antennaapparatus to perform diversity receiving operation in a receiving stateand causing the antenna apparatus, in a transmission state, to performtransmission with the directivity used in a receiving state.
 14. Thewireless terminal according to claim 12, wherein the control sectionperforms control operation for causing the antenna apparatus to performdiversity receiving operation in a receiving state and causing theantenna apparatus, in a transmission state, to perform transmission withdirectivity at which a maximum radiation direction of the antennaapparatus is oriented in a direction opposite a direction from thewireless terminal toward a user of the wireless terminal.
 15. An antennaapparatus comprising: a first substrate; a linear radiating elementplaced on a first plane which is one surface of the first substrate; aground conductor placed on a second plane which is the other surface ofthe first substrate; a first conductor which is placed, in parallel tothe radiating element, on the second plane while being electricallyisolated from the ground conductor; a first switch for connecting theground conductor to the conductor; and a control unit which controlsshort-circuiting/opening of the switch, wherein one of the groundconductor and the conductor is placed opposite the radiating element.16. The antenna apparatus according to claim 15, further comprising: asecond conductor placed at a position symmetrical to the first conductorwith respect to the ground conductor; and a second switch for connectingthe ground conductor to the second conductor, wherein the groundconductor is placed opposite the radiating element.
 17. The antennaapparatus according to claim 15, wherein reactance of the conductor isvariable.
 18. The antenna apparatus according to claim 15, wherein theconductor comprises: a plurality of conductor pieces divided into awidthwise direction thereof; and a third switch for connecting theplurality of conductor pieces.
 19. The antenna apparatus according toclaim 15, wherein the first switch comprises a plurality of switches forconnecting the ground conductor to the metal conductor at a plurality oflocations.
 20. The antenna apparatus according to claim 19, wherein thethird switch connects the ground conductor and the metal conductor,which are provided at positions opposite the vicinity of a maximumvoltage position on the radiating element.